smaller always better? , .684 vs. .688

[djinnform]

I've always used .688 Titanium Dye back with Evil, but noticed at lot of guys using .684 bore size for the same Evil paint at our field.

So I bought a .684 Dye digi cam, and used it all day, and never broke one ball.

But, I don't feel like the .684 is more accurate, in fact, it seems less accurate than my Titanium .688 Dye back.

Could this be?

[Patron God of Pirates]

The bore size will effect your consistency and efficiency, not your accuracy. Granted, greater consistency makes it easier to predict the flight path of your paint.

[OPBN]

The bore size will effect your consistency and efficiency, not your accuracy. Granted, greater consistency makes it easier to predict the flight path of your paint.

Yep. I use a Freak or J&J kit depending on the marker I am playing with and use the best bore to barrel match I can. I know there is the great debate on underboring, but I don't get into that much honestly.

[athomas]

Ideally, you want the bore size that causes the balls to lightly touch the barrel in two spots on opposite sides of the ball, usually at the seam. This will give you maximum consistency. Ultimately, consistency depends on having paintballs that are consistent. A larger bore is more forgiving than a smaller bore when it comes to paint that is not perfectly round. A larger bore also prevents barrel breaks due to weak seamed paintballs. The guys that are underboring for their paintball size, are depending on having good quality, consistent paintballs.

[Hook]

I exclusively underbore if I am playing pump with quality paint, such as Marbs. Usually works great efficiency-wise

[cockerpunk]

Ideally, you want the bore size that causes the balls to lightly touch the barrel in two spots on opposite sides of the ball, usually at the seam. This will give you maximum consistency. Ultimately, consistency depends on having paintballs that are consistent. A larger bore is more forgiving than a smaller bore when it comes to paint that is not perfectly round. A larger bore also prevents barrel breaks due to weak seamed paintballs. The guys that are underboring for their paintball size, are depending on having good quality, consistent paintballs.

that is actually the worst for consistency. and its because of inconsistently sized paintballs. we underbore exactly because paint is not consistent.

you see, at paint to barrel match, the barrel is a fixed size. meanwhile, every paintball is a different size (even good paint). so each ball is at a different place on the over to undebrore scale ... which means the drag to seal ratio is different for each ball, which means each one will come out a different speed. meanwhile, at a large overbore, every ball will not touch, so the drag to seal ratio will be very close on the balls. conversely, at a reasonable underbore, every ball will seal tight, so the drag/seal will be consistent, providing consistent velocity.

a large over or underbore will give you good consistency, with underboring .003-.005 being a bit more consistent. underboring is also much more efficient (up to 30 fps). paint to barrel match will be the worst consistency.

the answer to your question though OP is another one "what size is your paint" without knowing what size paint you are shooting, its impossible to tell you what bore size to use. my general rule of thumb is to aim for .003" to .005" underbore. i select this by blow testing the paint, and then when i find a match, use teh barrel 3 to 5 under it. we have not found underboring, even with extremely brittle paint, to break more paint until .007" - 009" underbore. so smaller is not always better, the reason underboring caught that bug was because before it was popular, getting barrels in the sizes to make a .003 to .005 underbore to work was nearly impossible due to shrinking paint. so we all cheered when the return of .679 and smaller barrels came out, as paint is consistently below .683 here.

using high speed videos from jack wood, and simon, and our own work, we have determined most "barrel breaks" are really minor damage to the ball during the loading cycle which later fail completely when subjected to the power pulse. a true "barrel break" where a perfectly normal, undamaged ball, breaks int he barrel is extremely rare, and has a distinctly different symptom to most "barrel breaks"

[Dark Side]

The bore size will effect your consistency and efficiency, not your accuracy.

How could you possibly believe this? Efficiency and consistency is directly tied to accuracy. Muzzle speed helps to dictate accuracy and you can even go so far to show that if improperly sized the paint will wobble in the barrel further decreasing accuracy.

[athomas]

that is actually the worst for consistency. and its because of inconsistently sized paintballs. we underbore exactly because paint is not consistent. No, I mentioned that the best consistency is if the ball touches on both sides of the ball but it depends on consistent paint. That is paramount. It takes much less energy to pop that cork as well, which makes it very efficient.

If you are talking inconsistent paint, then that is where we either underbore or overbore for increased consistency. I think we are talking the same language but you are interpreting my writing a bit differently. I suspect we are interpreting the amount of touch differently. What I interpret as the right amount of ball touching, you might be interpreting as a couple of thousands of underbore, in which case we are on the same page.

I remember back in 1990 when we were using PMI premium and were shooting barrels that were 0.690". The paint was popping like a cork and flying all over the place with no predicability. I was one of the only ones that had a barrel with known id sizes, and changed to a near perfect match at 0.6925". The balls flew perfect and consistent every shot. We checked the paint and found it to be consistent from ball to ball, so underboring by even 0.0025" was not working for us at that time.

As a personal preference, I like to overbore because I have less barrel breaks. This is even when I have sized the barrel for my paint. It is the one or two odd shaped balls in a bag of 500, that could cause a problem. I prefer not to take a chance when in a tournament environment and goo in my barrel could be the difference between winning and losing due to a missed shot.

[cockerpunk]

How could you possibly believe this? Efficiency and consistency is directly tied to accuracy. Muzzle speed helps to dictate accuracy and you can even go so far to show that if improperly sized the paint will wobble in the barrel further decreasing accuracy.

up to about a 15 fps spread, consistency does not effect accuracy.

[cockerpunk]

No, I mentioned that the best consistency is if the ball touches on both sides of the ball but it depends on consistent paint. That is paramount. It takes much less energy to pop that cork as well, which makes it very efficient.

If you are talking inconsistent paint, then that is where we either underbore or overbore for increased consistency. I think we are talking the same language but you are interpreting my writing a bit differently. I suspect we are interpreting the amount of touch differently. What I interpret as the right amount of ball touching, you might be interpreting as a couple of thousands of underbore, in which case we are on the same page.

I remember back in 1990 when we were using PMI premium and were shooting barrels that were 0.690". The paint was popping like a cork and flying all over the place with no predicability. I was one of the only ones that had a barrel with known id sizes, and changed to a near perfect match at 0.6925". The balls flew perfect and consistent every shot. We checked the paint and found it to be consistent from ball to ball, so underboring by even 0.0025" was not working for us at that time.

As a personal preference, I like to overbore because I have less barrel breaks. This is even when I have sized the barrel for my paint. It is the one or two odd shaped balls in a bag of 500, that could cause a problem. I prefer not to take a chance when in a tournament environment and goo in my barrel could be the difference between winning and losing due to a missed shot.

ALL paint is inconsistent. not only in its size, but also in how it is loaded, the orientation of that ball matters greatly to drag. paint to barrel is always going to be the worst for consistency because of this.

paint to barrel match has less friction, yes, but it also has a lot of leakage. this is why under-boring is much more efficient, yes there is more friction, but it makes a much better seal.

we describe paint to barrel match as the same thing, the blow test match ... so we are not talking about the same thing.

underboring, or paint to barrel match does not increase the frequency of barrel breaks until you get down to extreme underbores. that is old thinking, long been overturned. if you are getting barrel breaks, look at your loader, and look at your bolt.

[dboggs79]

Something being accurate is not the same thing as being precise.

[cockerpunk]

Something being accurate is not the same thing as being precise.

someone ALWAYS brings this up ... haha

for the purposes of paintball, accuracy and precision are interchangeable. this is because the aim point is easily changed.

this is not like a measuring system or device where there is a true value we are trying to hit, that "true value" is the aim point of the gun, and easily movable.

to bring up an example, if i had a target out at 30 feet, i could take the exact same setup and shoot it, and get zero hits (0% accuracy) and i could shoot it and get every one to hit (100% accuracy). only by moving the aim point. this doesn't mean in paintball terms that the setup has multiple accuracies, it means i have bad aim.

[Patron God of Pirates]

How could you possibly believe this? Efficiency and consistency is directly tied to accuracy. Muzzle speed helps to dictate accuracy and you can even go so far to show that if improperly sized the paint will wobble in the barrel further decreasing accuracy.

Lol. Way to quote only the part of my statement that supported this. You missed "Granted, greater consistency makes it easier to predict the flight path of your paint."

Question for those who do underbore? Do you use digital calipers? The only time I tried underboring the first ball only made it past the detent, The next ball engaged my LV.10 so I was fully jammed up. I've always used the paint to barrel matching technique outlined above by athomas and had (empirically) good results.

[dboggs79]

I had to...lol

[cockerpunk]

Lol. Way to quote only the part of my statement that supported this. You missed "Granted, greater consistency makes it easier to predict the flight path of your paint."

Question for those who do underbore? Do you use digital calipers? The only time I tried underboring the first ball only made it past the detent, The next ball engaged my LV.10 so I was fully jammed up. I've always used the paint to barrel matching technique outlined above by athomas and had (empirically) good results.

i undebrore on my cocker threaded mags, but i also don't tune my level 10 that hot. i already explained how i select my bore size.

works great, i can squeeze 1350 out of a 68/45 on a soft fill with a nice underbore. thats almost reasonable efficiency!

[athomas]

Question for those who do underbore? Do you use digital calipers? The only time I tried underboring the first ball only made it past the detent, The next ball engaged my LV.10 so I was fully jammed up. I've always used the paint to barrel matching technique outlined above by athomas and had (empirically) good results.Once the bolt gets past its level 10 small stem part, it will smash a ball into the breach regardless of if it wants to go or not, and then fire the contents of the ball out the front. If the ball only made it past the first detent, it is more likely a result of the level 10 bolt spring being too strong for your velocity setting than it is that the extra friction from the underboring is halting things. It is possible that the level 10 bump is just enough to push the ball forward and allow the next one to drop into the breach.

[Patron God of Pirates]

Once the bolt gets past its level 10 small stem part, it will smash a ball into the breach regardless of if it wants to go or not, and then fire the contents of the ball out the front. If the ball only made it past the first detent, it is more likely a result of the level 10 bolt spring being too strong for your velocity setting than it is that the extra friction from the underboring is halting things. It is possible that the level 10 bump is just enough to push the ball forward and allow the next one to drop into the breach.

That all makes perfect sense, but when I swapped out the freak insert for a larger (big enough to drop the paint through) one the problem went away. I came to the conclusion that the air blast escaped via the powerfeed tube.

[nak81783]

What I'm struggling with is one underbores to remedy inconsistencies in paint, but one must use that same inconsistent paint to determine which bore size to use. This can be applied to overboring as well.

If the blow-by is inconsistent if attempting to overbore, and the drag is inconsistent when attempting to underbore, does it truly make a difference?

What about coefficient of friction between a constant barrel and inconsistent paint? What about the ball deforming when the air blast hits it? Would that increase the seal of an inconsistent paintball within the barrel similar to an oring deforming into a seal when pressure is applied? Should we therefore aim for a -.001" underbore to +.001 overbore to get maximum seal, but minimum drag?

So many variables (especially when measuring to thousandths of an inch on gel capsules), but the only constant is the inconsistent paint.

Given all these and many other variables, get the paint to barrel match relatively close, and continue on the premise that paintball continues to be an accuracy by volume game.

Only exception would be for closed bolts, where the barrel is your detent, but that's a design influence not really relevant to the question at hand.

-Nathan

[cockerpunk]

What I'm struggling with is one underbores to remedy inconsistencies in paint, but one must use that same inconsistent paint to determine which bore size to use. This can be applied to overboring as well.

If the blow-by is inconsistent if attempting to overbore, and the drag is inconsistent when attempting to underbore, does it truly make a difference?

What about coefficient of friction between a constant barrel and inconsistent paint? What about the ball deforming when the air blast hits it? Would that increase the seal of an inconsistent paintball within the barrel similar to an oring deforming into a seal when pressure is applied? Should we therefore aim for a -.001" underbore to +.001 overbore to get maximum seal, but minimum drag?

So many variables (especially when measuring to thousandths of an inch on gel capsules), but the only constant is the inconsistent paint.

Given all these and many other variables, get the paint to barrel match relatively close, and continue on the premise that paintball continues to be an accuracy by volume game.

Only exception would be for closed bolts, where the barrel is your detent, but that's a design influence not really relevant to the question at hand.

-Nathan

oldest test we did: https://spreadsheets.google.com/pub?key=pp1UimQwRsMngwmAygIkHfQ

[GoatBoy]

There is a possible trend going on in those tests, but unfortunately the sample size per run is too small to be conclusive.

[cockerpunk]

There is a possible trend going on in those tests, but unfortunately the sample size per run is too small to be conclusive.

same sizes are 20+ shots each, more then large enough.

we have tons of data, as we also collect velocity on every shot we shoot in every test, so there is more then enough data. the control bore tests we later did show the exact same trend.

link to all the data: http://punkworkspaintball.com/index.php?p=2

[GoatBoy]

I haven't sifted through all of your data, but have you ever done a run of 100 and chrono'd every shot?

[cockerpunk]

I haven't sifted through all of your data, but have you ever done a run of 100 and chrono'd every shot?

we did in the break in test, yes.

n=20 is more then enough samples to establish a mean and standard deviation of a paintball setup. if n=20 isnt enough ... then every time you chrono, and you dont fire more then 20 balls over the chrono without adjusting, then you are being terribly irresponsible!

[GoatBoy]

we did in the break in test, yes.

n=20 is more then enough samples to establish a mean and standard deviation of a paintball setup. if n=20 isnt enough ... then every time you chrono, and you dont fire more then 20 balls over the chrono, then you are being terribly irresponsible!

OK, let me take a quick look at your break-in test.

People aren't looking for standard deviation when they do a safety chrono.

[nak81783]

oldest test we did: https://spreadsheets.google.com/pub?key=pp1UimQwRsMngwmAygIkHfQ

First, let me apologize if my post came off directed at any single individual or if it came off less tactful than intended.

Concerning the data, may I ask for the measurement sampling of the paintballs used in this test?


-Nathan

[cockerpunk]

OK, let me take a quick look at your break-in test.

People aren't looking for standard deviation when they do a safety chrono.

they should be.

[cockerpunk]

First, let me apologize if my post came off directed at any single individual or if it came off less tactful than intended.

Concerning the data, may I ask for the measurement sampling of the paintballs used in this test?


-Nathan

measurement sampling? how do you mean? of what?

[nak81783]

measurement sampling? how do you mean? of what?

I believe we have all mentioned paintball inconsistency. I assume the conclusions this data is expected to show are higher velocities and lower standard deviations for underbored barrels for a constant regulator setting. If so, I would want to see the diameters of the paintballs used - perhaps min/max diameter of each paintball fired - to see the paint/barrel match.

[cockerpunk]

I believe we have all mentioned paintball inconsistency. I assume the conclusions this data is expected to show are higher velocities and lower standard deviations for underbored barrels for a constant regulator setting. If so, I would want to see the diameters of the paintballs used - perhaps min/max diameter of each paintball fired - to see the paint/barrel match.

yes, we did not re-chrono the gun.

the size of the paintballs was established by blow test. min/max is not a very good measurement for paintball size in relationship to barrels. blowtest is actually ideal, because it measures directly the friction vs seal that defines the relationship between a ball and the barrel.

[GoatBoy]

they should be.

Yes and no. For the safety check they just do a quick check.

People should be maintaining their equipment and doing the longer run testing on their own time, not when there are 30 other people waiting behind them at the chrono station. Completely side issue.



If I'm reading your data correctly, that 7th column is a sliding window of standard deviation per the last 25 shots right?

Because if so, your data actually proves that 25 is not enough. Thanks for doing that. It's better to show you with your own data than with mine.

Let's just consider the last 100 shots as your earlier data is just too crazy to consider.

For the last 100 shots, the standard deviation is about 9.63.

If your sliding window standard deviation of 25 varies from 7 to nearly 12, that is way, way, way too much variance for these purposes.

If you redo that sliding window to 40 or 50, you'll see that the variance in standard deviation per window is way less; small enough to be useful.

[nak81783]

yes, we did not re-chrono the gun.

the size of the paintballs was established by blow test. min/max is not a very good measurement for paintball size in relationship to barrels. blowtest is actually ideal, because it measures directly the friction vs seal that defines the relationship between a ball and the barrel.

Respectfully, I truly appreciate what you've done, but a blow test is too subjective for me, especially with the earlier disagreement of what a blow test fit is/means. With a min/max diameter, one could establish a worst and best case seal or underbore condition. If the data still trended as it does now, factoring in the best and worst case, it would be a more objective study.


-Nathan

[cockerpunk]

Yes and no. For the safety check they just do a quick check.

People should be maintaining their equipment and doing the longer run testing on their own time, not when there are 30 other people waiting behind them at the chrono station. Completely side issue.



If I'm reading your data correctly, that 7th column is a sliding window of standard deviation per the last 25 shots right?

Because if so, your data actually proves that 25 is not enough. Thanks for doing that. It's better to show you with your own data than with mine.

Let's just consider the last 100 shots as your earlier data is just too crazy to consider.

For the last 100 shots, the standard deviation is about 9.63.

If your sliding window standard deviation of 25 varies from 7 to nearly 12, that is way, way, way too much variance for these purposes.

If you redo that sliding window to 40 or 50, you'll see that the variance reported standard deviation is way less; small enough to be useful.

i think you need to look at what that test was about ... the reason for the sliding average is because we were examining break-in. we were looking for how fast, if at all, the gun changes speeds when broken in. so you are comparing a brand new ... literally never fired gun changing speed when breaking in ... to a gun under normal operation, and then declaring that 20 shots is not enough. in one the gun is dynamic, in the other it is not. that makes no sense at all.

and again, for a safety check, if 20 shots doesn't give you a good average of the velocity, then we are all VERY VERY VERY unsafe right now. that means the 3 to 8 shots you fire over the chrono is not a good enough sample to establish the mean, and thus very unsafe ... by your definition of what is needed to compute an average. we should be shooting hundreds of shots over the chono to get a good average by your definition in this thread.

[cockerpunk]

Respectfully, I truly appreciate what you've done, but a blow test is too subjective for me, especially with the earlier disagreement of what a blow test fit is/means. With a min/max diameter, one could establish a worst and best case seal or underbore condition. If the data still trended as it does now, factoring in the best and worst case, it would be a more objective study.


-Nathan

its obvious you have not measured paintballs before, nor considered what paint to barrel match actually is.

1. the min to max diameter of a paintball, even a good one, can vary by as much as .020" inches. not kidding

2. the actual size of the paintball isn't the important part of its interaction with the barrel. the interaction with the barrel be summed up with two competing values ... the friction withe barrel, and the quality of the seal with the barrel.

now lets break that down:

friction: friction is obvious with the barrel, computed with the normal force (compression in this case) and the coefficient of friction. the coefficient of friction is largely irrelevant because it is a term in very computation, and is very similar between brands, so we can effectually ignore it. this leaves friction as essentially only related to the force of compression acting on it from the barrel. essentially, the amount the ball has to change to fit in the barrel. this is related to size, but also to orientation of the ball, and out of roundess of the ball.

seal quality: this is a function of the area gap between the footprint of the ball, and barrel. this is related to size, but also to orientation of the ball, and out of roundess of the ball.

so, the ratio of these two competing qualities is what determines the performance of a ball/barrel system.

so measuring the ball is largely a waste of time, unless you measure it in relationship to these two things. the blow test measures these two competing forces directly. because the human body cannot produce much beyond a few PSI, and the resualts are clear in terms of friction, this allows us to select the "blow test size" of a paintball. now the actual size as i said is essentially irrelevant, because again, the only thing that matters in this system is those two competing forces, as it is the only set of forces the ball ever sees in the barrel. and since we determine under vs overbore based on the blow test size, the conventions are all correct. blow test your paint, and then move down 3 to 5 thousandths for ideal performance.

[nak81783]

its obvious you have not measured paintballs before, nor considered what paint to barrel match actually is.

1. the min to max diameter of a paintball, even a good one, can vary by as much as .020" inches. not kidding

2. the actual size of the paintball isn't the important part of its interaction with the barrel. the interaction with the barrel be summed up with two competing values ... the friction withe barrel, and the quality of the seal with the barrel.

now lets break that down:

friction: friction is obvious with the barrel, computed with the normal force (compression in this case) and the coefficient of friction. the coefficient of friction is largely irrelevant because it is a term in very computation, and is very similar between brands, so we can effectually ignore it. this leaves friction as essentially only related to the force of compression acting on it from the barrel. essentially, the amount the ball has to change to fit in the barrel. this is related to size, but also to orientation of the ball, and out of roundess of the ball.

seal quality: this is a function of the area gap between the footprint of the ball, and barrel. this is related to size, but also to orientation of the ball, and out of roundess of the ball.

so, the ratio of these two competing qualities is what determines the performance of a ball/barrel system.

so measuring the ball is largely a waste of time, unless you measure it in relationship to these two things. the blow test measures these two competing forces directly. because the human body cannot produce much beyond a few PSI, and the resualts are clear in terms of friction, this allows us to select the "blow test size" of a paintball. now the actual size as i said is essentially irrelevant, because again, the only thing that matters in this system is those two competing forces, as it is the only set of forces the ball ever sees in the barrel. and since we determine under vs overbore based on the blow test size, the conventions are all correct. blow test your paint, and then move down 3 to 5 thousandths for ideal performance.

I have measured paintball diameters. I agree a single paintball can vary .020" or more in diameter depending on where the measurement is taken. I also agree orientation is important. If diameter can vary by .020" or more based on orientation, how can you quantify .003-.005" being a good underbore and .007-.009" to be too much of an underbore when even good paint, varying .020" in diameter for any single paintball, could meet either one of those conditions depending on how it orients in the breech/barrel?

I'm not saying you are right or wrong; I'm just saying the data is incomplete to convince me at this point.

I am sincerely enjoying this thread, and I mean for all of my responses to be respectful and mature. I sympathize, as it is often hard to be on the presentation side of data. I've been there many times. I simply want to discuss the data, not attack it.


-Nathan

[cockerpunk]

I have measured paintball diameters. I agree a single paintball can vary .020" or more in diameter depending on where the measurement is taken. I also agree orientation is important. If diameter can vary by .020" or more based on orientation, how can you quantify .003-.005" being a good underbore and .007-.009" to be too much of an underbore when even good paint, varying .020" in diameter for any single paintball, could meet either one of those conditions depending on how it orients in the breech/barrel?

I'm not saying you are right or wrong; I'm just saying the data is incomplete to convince me at this point.

I am sincerely enjoying this thread, and I mean for all of my responses to be respectful and mature. I sympathize, as it is often hard to be on the presentation side of data. I've been there many times. I simply want to discuss the data, not attack it.


-Nathan

what i am saying is the actual measurement of a paintballs size is not a very good determination for what bore size it is.

this is why i most often refer to paint in "blow test size" not actual physical size. because the blow test functional size is the only one that actually matters.

[GoatBoy]

i think you need to look at what that test was about ... the reason for the sliding average is because we were examining break-in. we were looking for how fast, if at all, the gun changes speeds when broken in. so you are comparing a brand new ... literally never fired gun changing speed when breaking in ... to a gun under normal operation, and then declaring that 20 shots is not enough. in one the gun is dynamic, in the other it is not. that makes no sense at all.

I figured as much.

Do you have a string of 100 shots on a non-breaking-in-gun so that I can re-make my point?

Again, I'd rather do it with your data than mine.




and again, for a safety check, if 20 shots doesn't give you a good average of the velocity, then we are all VERY VERY VERY unsafe right now. that means the 3 to 8 shots you fire over the chrono is not a good enough sample to establish the mean, and thus very unsafe ... by your definition of what is needed to compute an average. we should be shooting hundreds of shots over the chono to get a good average by your definition in this thread.

For starters, you assume I do think we're safe. Let's... stop bringing side issues into this and just talk about standard deviation.

I haven't eyeballed the minimum number of shots needed to get a decent average.

Average and standard deviation are not the same thing. It is entirely possible to arrive at a decent average at some number of shots, but still not have enough shots to get a decent standard deviation.

I am speaking to standard deviation directly.

Again, this point can probably be made if you point me at your data for a longer run of shots.

Just looking at your breaking-in-data which you don't want to accept as valid, but let's look at it anyways:

At shot 512, the STDEV was 7.91, and the average was like 248.

On the other end of the range, shot 447 had STDEV of 11.64, but the average... was 243.

So 25 shots might be good enough for average, but the STDEV varies so much as to not be useful.

[cockerpunk]

I figured as much.

Do you have a string of 100 shots on a non-breaking-in-gun so that I can re-make my point?

Again, I'd rather do it with your data than mine.

in that same data set, after the first 150 or so shots, all the way through 10 cases is the data you are looking for.

For starters, you assume I do think we're safe. Let's... stop bringing side issues into this and just talk about standard deviation.

my point was to illustrate the absurdity of 20 shots not being enough to find meaning, as every single day at every paintball field in America, far fewer shots are used to determine if people will have the gift of sight after playing paintball. i don't think that is a side issue.

I haven't eyeballed the minimum number of shots needed to get a decent average.

Average and standard deviation are not the same thing. It is entirely possible to arrive at a decent average at some number of shots, but still not have enough shots to get a decent standard deviation.

yup, i agree

I am speaking to standard deviation directly.

Again, this point can probably be made if you point me at your data for a longer run of shots.

Just looking at your breaking-in-data which you don't want to accept as valid, but let's look at it anyways:

you miss understand me ... the changes in velocity in the break in data are all explained quite easily. after the first 150 shots, the gun ran like clockwork, and we have tons of chrono data on it showing that 20 shots is more then enough to determine statistics.

At shot 512, the STDEV was 7.91, and the average was like 248.

On the other end of the range, shot 447 had STDEV of 11.64, but the average... was 243.

So 25 shots might be good enough for average, but the STDEV varies so much as to not be useful.

you can see where that number comes from, that 267 on shot 442 dragging the st dev up. i wonder if you can tell why that is .... i know why ...


alright, we can argue about st dev all day, and im happy to do that. but lets establish then a common ground ... we both agree 20 shots is effective at establishing the average of a sample. yes? this means then we can agree from the data set about the efficiency of barrels, yes? we can agree that under boring is more efficient. cause that is half the battle right there.

alright ....

ill give you consistency is a tricky one, if you note in the first test data, two .687 freak inserts shot quite different consistencies ....

[nak81783]

what i am saying is the actual measurement of a paintballs size is not a very good determination for what bore size it is.

this is why i most often refer to paint in "blow test size" not actual physical size. because the blow test functional size is the only one that actually matters.

So I'm trying to get on board with this. I took five paintballs and rolled them around at the top of various barrel inserts until they dropped in and I could blow them through. Using that same barrel insert that all five paintballs blew through, I then paid close attention to orientation. Since seams are typically the widest point of a paintball, I tried that first. I could only get three of the five to blow through with the seams acting as seals. Should I use the roll orientation method that got the five to go through, or the widest point method and size up until they all blow through. Then size down the .003-.005" you recommend?

The problem I have with this is chambering orientation is completely random. So no matter what method I use for the blow test, I could swing from underboring to overboring (or extreme conditions of either) given the paintball inconsistencies. This is why I stated earlier to get it relatively close, and fire away, hoping the paintball chambering orientation gods are on your side that day.

Thoughts?

[athomas]

When you measure the size of a paintball for the purpose of determining a bore size, always measure the seam. That will always be the largest diameter. Any barrel you select at that size will always touch on two points. So, if you physically measure each paintball, you can accurately select ones that are consistently sized. Of course, this depends on the paint being in good condition and round. Any paint that is not round won't work like that but should not be used for testing anyway. You can determine that by measuring the balls at two points on the seam at 90 degree angles from each other. Any measured values that are noticeably different should have that paintball tossed out of the test.

[nak81783]

athomas: Any given barrel size essentially acts like a go/no-go gage. Fit testing at the seams seems most logical. However, orientation changes could lead to extreme overboring, and paintball inconsistencies could lead to extreme underboring. I would think you would not want to throw out the out of round paint unless you are going to sort your entire supply. As you stated earlier, if you don't account for those few fliers, they could become an issue.

cockerpunk: Do you see any validity to repeating your test, performing your blow test with properly oriented seams, noting that bore size, and then gradually decreasing bore size until you do start to see obvious evidence of underboring causing barrel breaks? Perhaps you could do this with economy, mid, and high level paints from a few different companies. This could lead to a very repeatable procedure of what the average player should do and expect given a certain quality of paint, and the degree of underboring that could be safely used. Do whatever sample size you feel is appropriate for average and standard deviation (I see n=30 tossed around a lot), but I would be more concerned with quality X paint breaks Y balls out of a pod/hopper/bag/case/etc. with Z level of underboring. You may want to show barrel breaks going two or three inserts in the overbore direction as well just to cover everything. I think all this in a single chart, would let each individual decide on consistency, efficiency, and relative risk for their personal preference.

I didn't get a chance to look through all the other data you linked earlier. Maybe you already have this.

[athomas]

athomas: Any given barrel size essentially acts like a go/no-go gage. Fit testing at the seams seems most logical. However, orientation changes could lead to extreme overboring, and paintball inconsistencies could lead to extreme underboring. I would think you would not want to throw out the out of round paint unless you are going to sort your entire supply. As you stated earlier, if you don't account for those few fliers, they could become an issue.No matter what the orientation, you'll always have two points of contact if the paint is properly sized. Don't throw out the paint that is not round. Just don't use it for testing purposes. It throws off the results.

Other than that, if you know you have imperfect paint, you need to expect inconsistent shooting. Now you have to deal with it using a method you are comfortable with. Perhaps you should measure a large sample of balls and determine the smallest diameter of contact and use that as your barrel size. Then, every other ball will be using an underbore. Or, do the same using the largest measured diameter, except use an overbore. Personally, I use an "extreme" overbore. I sacrifice efficiency, but my shot consistency is good.

[nak81783]

Always having two points of contact is agreed upon, until you start compressing the ball, at which point those two points become larger "point" surfaces, and eventually "line" surfaces around the entire circumference.

Given the previous statement that accuracy is unaffected by consistency up to around 15fps (although a relative statement, I tend to agree with it, because "aiming" inconsistency is a much larger factor), are we really just talking about efficiency? If I recall correctly, any insert in cockerpunk's data was below a 7.5fps st dev. And if consistency leads to nothing more than accuracy, but all inserts produce an acceptable consistency, should we really just be comparing efficiency vs. potential ball breaks?

[GoatBoy]

alright, we can argue about st dev all day, and im happy to do that. but lets establish then a common ground ... we both agree 20 shots is effective at establishing the average of a sample. yes? this means then we can agree from the data set about the efficiency of barrels, yes? we can agree that under boring is more efficient. cause that is half the battle right there.

alright ....

ill give you consistency is a tricky one, if you note in the first test data, two .687 freak inserts shot quite different consistencies ....


I can't agree to anything that isn't backed by data, and that includes efficiency.

For average velocity, 20 is probably fine, judging by the data.

For standard deviation in velocity, 20 does not appear to be fine when the possible error in the standard deviation resulting from a sampling of 20 shots is potentially on the same scale as the trend that you were trying to indicate.

I ran some numbers with my own data, I will plug yours in once I figure out which data of yours you're willing to accept. Like I said originally, I looked at the last 100 of your first 500 because the previous shots were probably going crazy. Sure, you'll get an errant shot every now and then. That's what a larger sample is supposed to smooth over. Errant shots, and the probability of hitting a particularly bad run which is not reflective of the overall deviation, either on the + or - side. Shorter runs have a higher probability of showing up.

I did a run of 100 shots, same paint, same barrel, two different guns. (My testing was actually targeting efficiency.) I also generated random numbers with a similar FPS variance. Here's what it looks like:

Automag:
Window size 10, stdev variance 8.871928-2.936362=5.935566, mean variance 8.400000
Window size 20, stdev variance 6.990783-4.148240=2.842543, mean variance 5.700000
Window size 30, stdev variance 7.515195-4.657092=2.858103, mean variance 2.666667
Window size 40, stdev variance 6.978171-5.118844=1.859327, mean variance 1.750000
Window size 50, stdev variance 6.476457-5.346599=1.129857, mean variance 1.460000
100 shot (mean, stdev) = (284.24, 6.171161343153523)
Spyder:
Window size 10, stdev variance 8.875059-3.335000=5.540059, mean variance 9.800000
Window size 20, stdev variance 8.041177-4.073018=3.968159, mean variance 6.250000
Window size 30, stdev variance 7.793381-4.508485=3.284896, mean variance 5.600000
Window size 40, stdev variance 7.330302-5.196399=2.133903, mean variance 3.600000
Window size 50, stdev variance 6.867136-5.502838=1.364298, mean variance 2.400000
100 shot (mean, stdev) = (291.15, 6.189556208695906)
Random (100):
Window size 10, stdev variance 7.241854-3.326660=3.915194, mean variance 9.000000
Window size 20, stdev variance 6.863327-5.369505=1.493823, mean variance 4.600000
Window size 30, stdev variance 6.662987-5.476806=1.186182, mean variance 2.933333
Window size 40, stdev variance 6.587478-5.858098=0.729381, mean variance 2.475000
Window size 50, stdev variance 6.610320-5.842979=0.767340, mean variance 1.840000
100 shot (mean, stdev) = (285.48, 6.179928409902099)

Full data set is here:

https://docs.google.com/spreadsheet/ccc?key=0AtUb05cFvbYmdGpYZWFPOFJrci1Za2FEdFFxSU5vY kE&usp=sharing

And the python script I used for the calcs I can make public too; it's pretty trivial though.



The upshot is kind of obvious: the larger a window you take, the better the variance in the resulting standard deviation is.

How large a sampling is large enough? It's a matter of scale between the possible error in standard deviation, and how big the trend that you're trying to spot is.

If the possible swing in your results is larger than your trend, it's hard to say your results are conclusive.

[cockerpunk]

So I'm trying to get on board with this. I took five paintballs and rolled them around at the top of various barrel inserts until they dropped in and I could blow them through. Using that same barrel insert that all five paintballs blew through, I then paid close attention to orientation. Since seams are typically the widest point of a paintball, I tried that first. I could only get three of the five to blow through with the seams acting as seals. Should I use the roll orientation method that got the five to go through, or the widest point method and size up until they all blow through. Then size down the .003-.005" you recommend?

The problem I have with this is chambering orientation is completely random. So no matter what method I use for the blow test, I could swing from underboring to overboring (or extreme conditions of either) given the paintball inconsistencies. This is why I stated earlier to get it relatively close, and fire away, hoping the paintball chambering orientation gods are on your side that day.

Thoughts?

then .003 to .005 works well because you don't have to be that close in your blowtesting. because every ball will stick in a .005 even if your blow test was off by .002. in reality though, we have a limited number of bores to test, so that becomes the problem with the blow test.


athomas: Any given barrel size essentially acts like a go/no-go gage. Fit testing at the seams seems most logical. However, orientation changes could lead to extreme overboring, and paintball inconsistencies could lead to extreme underboring. I would think you would not want to throw out the out of round paint unless you are going to sort your entire supply. As you stated earlier, if you don't account for those few fliers, they could become an issue.

cockerpunk: Do you see any validity to repeating your test, performing your blow test with properly oriented seams, noting that bore size, and then gradually decreasing bore size until you do start to see obvious evidence of underboring causing barrel breaks? Perhaps you could do this with economy, mid, and high level paints from a few different companies. This could lead to a very repeatable procedure of what the average player should do and expect given a certain quality of paint, and the degree of underboring that could be safely used. Do whatever sample size you feel is appropriate for average and standard deviation (I see n=30 tossed around a lot), but I would be more concerned with quality X paint breaks Y balls out of a pod/hopper/bag/case/etc. with Z level of underboring. You may want to show barrel breaks going two or three inserts in the overbore direction as well just to cover everything. I think all this in a single chart, would let each individual decide on consistency, efficiency, and relative risk for their personal preference.

I didn't get a chance to look through all the other data you linked earlier. Maybe you already have this.

yup:

http://punkworkspaintball.com/index.php?p=7&id=6

in this test we tested over, under, and bore matched, and found nothing of statistical significance in our breakage. sure, our sample sizes were not ideal, but we shot literally all day, out of that gun over 9000 rounds, and what we found was all barrels will break paint.

this pointed us to barrels not really being the cause of barrel breaks.

now, i'd love to shoot until we had something like 20 breaks out of each barrel too, but using those numbers, that would be something on the order of 6 cases from each barrel, and something like 4 days of shooting. sorry, we can't do that.

https://spreadsheets.google.com/pub?key=t1P1KlZM-B7_CqEMklBz7xQ&output=html

in this test we looked at insane underbores ... up to .018 or so. we did not start seeing breakage until .012+ so a minor .005" like above just isn't dangerous.

[cockerpunk]

I can't agree to anything that isn't backed by data, and that includes efficiency.

For average velocity, 20 is probably fine, judging by the data.

For standard deviation in velocity, 20 does not appear to be fine when the possible error in the standard deviation resulting from a sampling of 20 shots is potentially on the same scale as the trend that you were trying to indicate.

I ran some numbers with my own data, I will plug yours in once I figure out which data of yours you're willing to accept. Like I said originally, I looked at the last 100 of your first 500 because the previous shots were probably going crazy. Sure, you'll get an errant shot every now and then. That's what a larger sample is supposed to smooth over. Errant shots, and the probability of hitting a particularly bad run which is not reflective of the overall deviation, either on the + or - side. Shorter runs have a higher probability of showing up.

I did a run of 100 shots, same paint, same barrel, two different guns. (My testing was actually targeting efficiency.) I also generated random numbers with a similar FPS variance. Here's what it looks like:

Automag:
Window size 10, stdev variance 8.871928-2.936362=5.935566, mean variance 8.400000
Window size 20, stdev variance 6.990783-4.148240=2.842543, mean variance 5.700000
Window size 30, stdev variance 7.515195-4.657092=2.858103, mean variance 2.666667
Window size 40, stdev variance 6.978171-5.118844=1.859327, mean variance 1.750000
Window size 50, stdev variance 6.476457-5.346599=1.129857, mean variance 1.460000
100 shot (mean, stdev) = (284.24, 6.171161343153523)
Spyder:
Window size 10, stdev variance 8.875059-3.335000=5.540059, mean variance 9.800000
Window size 20, stdev variance 8.041177-4.073018=3.968159, mean variance 6.250000
Window size 30, stdev variance 7.793381-4.508485=3.284896, mean variance 5.600000
Window size 40, stdev variance 7.330302-5.196399=2.133903, mean variance 3.600000
Window size 50, stdev variance 6.867136-5.502838=1.364298, mean variance 2.400000
100 shot (mean, stdev) = (291.15, 6.189556208695906)
Random (100):
Window size 10, stdev variance 7.241854-3.326660=3.915194, mean variance 9.000000
Window size 20, stdev variance 6.863327-5.369505=1.493823, mean variance 4.600000
Window size 30, stdev variance 6.662987-5.476806=1.186182, mean variance 2.933333
Window size 40, stdev variance 6.587478-5.858098=0.729381, mean variance 2.475000
Window size 50, stdev variance 6.610320-5.842979=0.767340, mean variance 1.840000
100 shot (mean, stdev) = (285.48, 6.179928409902099)

Full data set is here:

https://docs.google.com/spreadsheet/ccc?key=0AtUb05cFvbYmdGpYZWFPOFJrci1Za2FEdFFxSU5vY kE&usp=sharing

And the python script I used for the calcs I can make public too; it's pretty trivial though.



The upshot is kind of obvious: the larger a window you take, the better the variance in the resulting standard deviation is.

How large a sampling is large enough? It's a matter of scale between the possible error in standard deviation, and how big the trend that you're trying to spot is.

If the possible swing in your results is larger than your trend, it's hard to say your results are conclusive.

i disagree on the grounds that we have been testing barrels for 5 years ... and EVERY SINGLE TIME we end up with the same conclusion. that repeatability is a sure sign of data convergence. anyone can do it themselves at there own field too

i like that your testing things though, please come by punkworks and post up what you are working on! more data = more better ALWAYS.

[nak81783]

Why not? I'll give it a shot.

Blow test with seams engaging the barrel ID. Then downsize .003-.005" (or closest increment down).

But if I get bunkered in the back while swabbing out a messy barrel...

[cockerpunk]

Why not? I'll give it a shot.

Blow test with seams engaging the barrel ID. Then downsize .003-.005" (or closest increment down).

But if I get bunkered in the back while swabbing out a messy barrel...

you'd be cleaning out that barrel either way. most barrel breaks are a function of the loading system and the ball/bolt/breach interaction, not the ball/barrel interaction.

[Frizzle Fry]

Cockerpunks tests do not account for several important factors that he refuses to acknowledge.

[nak81783]

Cockerpunks tests do not account for several important factors that he refuses to acknowledge.

Please elaborate, or link me to past discussions.

[cockerpunk]

Cockerpunks tests do not account for several important factors that he refuses to acknowledge.


Please elaborate, or link me to past discussions.

Frizzle can only ever be that vague.

is our testing incomplete? you bet. all testing, of everything is incomplete. thats why we still don't know everything there is to know.

but that doesn't mean its not useful, or we cannot learn to improve performance from it. i've been underboring for 4 or 5 years, as have many many other folks. and as i said, esp on our automags ... the extra efficiency is a godsend.

[GoatBoy]

i disagree on the grounds that we have been testing barrels for 5 years ... and EVERY SINGLE TIME we end up with the same conclusion. that repeatability is a sure sign of data convergence. anyone can do it themselves at there own field too

Then what you are talking about is a much larger aggregate of five years worth of data which represents effectively more shots. Which is fine, that is a way to tackle the problem. That data should be better collated or something -- you can't just point to some strings of 20 shots and expect a rational person to accept a conclusion regarding the standard deviation effectively. Based on that immediate data. I'm not disagreeing with your possible trend. I have no data either way.

Your five years of testing, however, has not proven that 20 shots alone is enough. Look at your data, look at my data, look at anyone else's data where you can pick a random run of 20 and compare it against the aggregate longer run. The data strongly shows that if you're looking for differences like what were indicated in that bore test, 20 shots is not enough.



i like that your testing things though, please come by punkworks and post up what you are working on! more data = more better ALWAYS.

Likewise, I appreciate your testing, I just... man, I wish I had the resources you guys have. I get to do everything myself, without proper facilities, without good equipment access, and without pretty much any assistance because quite frankly nobody quite understands what I'm doing anyways. That's why I can't tolerate errors in my own testing. It's literally too painful to go and redo it.

Trying to limit my forum exposure though. I'm actually probably going to start contracting it...

[djinnform]

Thanks for all the great info. guys.

I shot 3/4 a case of paint yesterday through the .684 back, (no breaks) and the needle on my air tank barely moved. I used the air from last week! So, I'm pretty sure that the smaller bore increased my air efficiency to a noticeable difference at this point. But, my gut feeling is that the .688 is still slightly more accurate, but slightly less air efficient. Next time I play, I will switch back to the .688 and report back.