smaller always better? , .684 vs. .688

[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?...sMngwmAygIkHfQ

[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?...sMngwmAygIkHfQ

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.