What really makes the perfect barrel?

[hitmanng]

As some of you know I was never a fan of the freak or the concept of a step bore barrel. Strangely enough although I still do not have any evidence, the empiric evidence speaks for itself. Matching paint to the barrel does make a difference. So my question is what makes the perfect barrel.
I discussed this tonight with my Grandfather that owned a metal shop for many years and is an accomplished gunsmith. He has not investigated paintball but we did talk about some concepts.
OK now the questions.
What is the #1 factor? My guess is perfection in smothness and straightness. Any imperfection has the ability to throw off the ball. So why do I never hear about people honing their barrels?
How important is size matching and which way is better to big or to small and how close is good enough? From what I see we are talking thousanths. 0.687, 0.689 Too big the ball bounces according to the talc test and too small the ball is compressed and as it decompresses may not fly straight.
Does the nubbin/ball detent mess up the flight? None of us want to see the ball roll down the barrel but are we hurting ourself here?
Are step bore barrels more accurate and why? This is definatly a new trend but why, is it the old transition into the atmospheric air myth or what?
2 part barrels and are the tread really straight? The trend for multi-bore barrels is 2 parts, but the margin for error seems to increase with screwing things together or thin inserts. How much more expensize is it to make 6 barrels instead of a front and 6 backs?
Rifling does not work what else might? what if you had 3 small (micro) ridges like 0.0005 to 0.001 on three sides of the barrel. Could you eliminate the need for diffent bore sizes by compressing less of the paintball without losing much gas efficiency. Could you backspin the ball by creating a groove under it that the air would escape through.

I would like to talk tht physics of friction, how smooth is smooth enough, what really does happen when a large painball exits a small bore barrel. Share your thoughts and knowledge.

Respectflly,
Gordon Mann
Hitmanng

[ckyguy]

first of all, how i determine what barrel to use is just by placing a ball in the barrel, and simply seeing if it rolls down the barrel, if it does then the paint is too small, if i can't blow the ball through, the ball is too big, if it doesn't roll out of the barrel but will be blown out, it seems to be a good paint match.

I agree with you that the perfection of smoothness is probably the most important factor in accuracy, and im pretty sure the reason you dont see many people honing barrels is because most barrels are honed very well in the factory.

The big reason why a good bore-paint match is important is because you want an even gas flow all around the ball to provide as little friction as possible because friction slows down the fps, increasing pressure needed to propel it, and also makes a more accurate flight having 0 resistance. You want as close of a match as possible to have as little air flowing around the ball as possible, throwing off accaleration and many other elements of a balls accuracy. I think it would be better to have a ball too small for the barrel than too big because if it's too big 1. it's goin to take more gas to push it through, or 2. it's goin to break in the barrel, the only downside to having a ball too small is that the paint won't be as accurate.

The nubin/ball contact should have very little, if any effect on spinning the ball.

I also agree with you that threaded barrels in theory would have a great % error of becomming even slightly bent, even if its not seen by the naked eye, especially the freak system with the very thin bore inserts, and also when you break paint in a 2-peice barrel, its much harder to clean out than a 1-peice.

Friction from the ball to barrel is a big factor too, thats why better barrels on the market have nice coatings on the inside to reduce friction, with the exception of stainless barrels that already are friction-free.

[hitech]

Random vortex shedding causes approx. 2Gs worth of laterial force on the paintball in flight. Good luck finding anything that makes a significant impact on that.

[Wat]

Funny Hitech

But seriously, when it comes to barrel accuracy and basically any sort of paintball improvement discussions, people always seems to forget that there is variance in paint.

Even within one box of paint you are not going to find the same size balls. I once had a case of paint where different balls could fit perfectly in the second largest or the second smallest freak insert. There is no point having inserts in 0.002" increments if your paint varies by 0.005". I should actually get calipers one of these days but has anyone measured the freak inserts? They don't look particularly rigid to me.

Barrels are hype driven. There is no need for carbon fibre, titanium, tungsten, ceramics or any exotic sounding name. Some of the best barrels out there are brass.

Personally, i think that a mid and large bore barrel will suit 80% of the paint out there. Toss in a tiny bore barrel and that will give you 99% coverage.

[hitech]

Originally posted by Wat
Funny Hitech
I take it you haven't read this:

http://www.automags.org/forums/showthread.php?s=&threadid=64669

[hitmanng]

Hello Hitech,
I actually read the entire thread and responded to it just yesterday. It took me hours. I have copied my response here from that thread since it has gotten no response there. While you have proven that there is a randomness generated, that is on top of the issue of accuracy in the shot vector as the paintball leaves the barrel. Here is a copy of my post:



Hi All,
I haven't talked about any of this since Deep blue was the fight club,we discussed reynolds factors and turbulence even back then.
I think there is a big part of the equation that is being missed. You have analysed until you are deep blue in the face what happens durring 99.5% of the paintball flight. That once you have a sphere traveling at 280fps, with the current wt of a paintball, you are going to have a certain level of randomness imparted by the turbulence behind the ball. I for one stand up and say bravo. You have explicitly defined something that we cannot change unless we play in a vaccum (deadly), or fundimentally change the paintball (not likely).
You have also effectively eliminated the need for people to worry about spin/rifleing unless the paintball gets heavier, changes shape, or we shoot it a lot faster.

I think Glenn's problem with all of this (not speaking for him of course), and mine, is that we are in an amazing way ignoring that first 12 inches of the balls travel. At this time we are not looking at the simple fluid dynamics of a ball. I am talking about what happens in the marker and in the barrel before it exits and the effect this has on the tragectory of the ball within the barrel and upon its immeadiate exit from the barrel.
This leads us away from much of Tom's data as he used the same gun and barrel for every shot and it was locked in a vise. This means he removed all of the parameters that we can effect and change to improve accuracy. All that was left was the randomness of air currents (Sorry Tom, not meaning to burst this scientific bubble, but I am the Slayer of scared cows, even yours).

So what matters the first 12 inches? Look at what we have.
1. We have a wall of force (air) accelerating the ball into the atmospheric air(no trailing currents there folks) and in some way disipating. Ok, that is why Tom created the Crown point barrel (he must have thought it mattered) and others created the ported barrel. If the barrel is ported and long enough the issues of the initial push may be eliminated (maybe longer barrels are more accurate).
2. We have the barrel. The ball is traveling through the barrel with forces places upon it. One is the force excellerating it, another is the force of the barrel pushing on a larger ball, or the force of the air passing the ball for a smaller ball.
3. We have a moving marker. I know you may think that doesn't matter but we know that a ball can ricochet around in the barrel from Tom's barrel tips and the talc test. The barel might not be perfectly straight or aligned or you may be moving it.
And doing the math:


The diameter of the paintball is 0.68 approx I am not sure of the bore of a 2 step
barrel but let us assume 0.7. If the ball is going down the exact center (which I highly doubt considering manufacturing tolerences) that leaves 0.01 inch that the barrel would have to move. The ball is only in the barrel for about 0.006 seconds.
Thats 0.01 inch divided by 0.006 seconds = 1.66 inches per second. All it takes is moving your barrel 0.01 inches at a rate faster than 1.6in/sec. That is while shooting 6 bps of perfect balls out of a perfect barrel to have a hit. I think maybe it hits more than you think.
Extrapolated From: http://www.automags.org/ubb/Forum4/HTML/000019.html

So what who cares?.... Well you do. These are all elements you can change. They effect what direction the paintball is heading then it leaves the barrel.
So lets say our shot vector is one degree off straight when it leaves the barrel. At 5 feet it is 1 inch off mark, at 50 feet it is 10 inches off mark. Let us say our shot vector is at an angle of 0.5 degrees off center when it exits the barrel. That's 0.5 inch at 5 ft, and 5 inches at 50 ft, and 10 inches off mark at 100ft.

Maybe I am full of it maybe all paintballs leave all barrels and all guns at exactly the same angle. And maybe we always shoot with our gun in exactly the same position, and maybe we never move even 0.01 inch at a rate of 1.6in/sec while taking a shot.

I enjoyed the read on this post it was incredible. Keep up the good work. Now lets look at the other 0.5% of the game and maybe that will make all the difference.
Respectfully,
Your Friend
Hitmanng

I hope this clears up why I am addressing this issue.
Respectfully,
Hitmanng

[hitech]

Hey there Hitmanng,

Okay, a one degree deviation is big. Also, for your numbers to be accurate the flight path of the paintball needs to be straight and true. I think we can all agree that it is anything but. There are approx. 2Gs worth of random lateral force applied many, many times as the paintball flies down range. There just isn't anything else that a barrel can do that will have any kind of significant impact on that. The only thing that has been suggested that "could" make a difference is how spin affects the shedding of vortices. I know of no research into this and the data appears to imply that it has very little affect.

Respectively,
Hitech

[Wat]

Nope, haven't actually read that link HiTech. I wasn't laughing because i thought you were BSin, was just laughing at the terseness of the response.

Am not adequately caffeinated to read that thread, but i do know what vortex shading is. Got my mech e degree from MIT in 97, took a year of thermo/fluids and once or twice even went to class.

The funny thing is that while you can use all sorts of math to understand the forces acting on the paintball, all you can really do is calculate expected trajectory / range. Like you said, there's very little you can do to actually alter / improve that.

[hitech]

Originally posted by Wat
[BI wasn't laughing because i thought you were BSin, was just laughing at the terseness of the response.
[/B]

Yeah, I probably should explain just a little more. It's just that I have said that so many times that I am tiring of it. ;) I sometimes forget that not everyone reads everything I post (not that I know why not). ;)

[hitmanng]

Originally posted by hitech
Hey there Hitmanng,

Okay, a one degree deviation is big. Also, for your numbers to be accurate the flight path of the paintball needs to be straight and true. I think we can all agree that it is anything but. There are approx. 2Gs worth of random lateral force applied many, many times as the paintball flies down range. There just isn't anything else that a barrel can do that will have any kind of significant impact on that. The only thing that has been suggested that "could" make a difference is how spin affects the shedding of vortices. I know of no research into this and the data appears to imply that it has very little affect.

Respectively,
Hitech

I hope to convice you that you are wrong on this. Let's start with a standard shot pattern at 60ft like in Tom's Data.
http://members.aol.com/hitmanng/paintball/smtarget.jpg

I realize this is a random shot pattern but it is random within a certain defined area that the trailing vortexes can create. Let us say a 6 inch distribution for arguments sake. Now let us say I find something in the barrel that can shift this shot pattern 2 inches. Now here would be the distribution on the shot pattern 2 inches off in 4 axises.
http://members.aol.com/hitmanng/paintball/lgtarget.jpg

Note that the shot pattern is nearly doubled.
So you say nothing can do that. In researching paintballs and bore sizing I have found that Paintball size range 0.676 to 0.692. Barrel bores range in size from Barrels 0.682 to 0.694. Paint also ranges in size within a bag and based on humidity. Let us assume it is possible that we have a barrel that is 0.01 larger than the paint we are using. If it starts on one side of the barrel and ricochets down the barrel and hits using simple reflection only 2 times on the way down the barrel,
http://members.aol.com/hitmanng/paintball/bounce1.jpg
It will exit the barrel at an anlge of 0.143 degrees. It will show the exact shot pattern deviation in the above graphs.
Now in Tom's Bore tips he writes:
Tom Kayes:

If the barrel is too big, the ball ricochets back and forth down the tube. We used to say it looked like Zebra stripes in there. Hence big barrels do NOT create an "air bearing". Barrels that are too small scrape most of the powder off and this creates excessive FRICTION."

Now I assume Zebra stripes means it hit more than once on each side. Let us double that number and say twice on each side. The angle increases to 0.288 and the shot pattern increases to 3 inches off in each direction. If you decrease the excess space to 0.005 in on the bore and increase to 6 hits on each side you get the same data.

I realize that simple reflection does not take place but I think should should be compelling enough to indicate that better bore match will decrease your shot distribution.
This is not new information in the US Naval Ordinances and Gun Barrel Construction guide where it talks about old cannons it states "There were other reasons, too, for the inaccuracy of early gunnery. ...close clearances would have made loading impossible, the shot was a fairly loose fit.
When the gun was fired ...much of the gas would blow by one side or the other. The result was that a lot of the gas pressure was wasted because it didn’t serve to propel the ball, and as the ball left the muzzle it was not likely to be traveling along the bore axis."

I have seen many gun reviews and they all have different shot dispersals. I have also seen many barrel reviews and have seen many shot dispersals. Genneral 6 inches is the best it can get but I would rather have 6 inches than 12 inches.

Hitmanng

[hitech]

It appears that my post to this was somehow lost. I'll try again, but it is never as good the second time around. ;)



I realize this is a random shot pattern but it is random within a certain defined area that the trailing vortexes can create. Let us say a 6 inch distribution for arguments sake. Now let us say I find something in the barrel that can shift this shot pattern 2 inches.
The problem is that I do not believe that there is ANYTHING you can find that will make anywhere near a 2 inch difference. BTW, Tom spent hundreds of thousands of dollars trying to find something that significant. He never found anything. The easy things have already been tried. ;)



So you say nothing can do that.

Um, yeah. ;)



Let us assume it is possible that we have a barrel that is 0.01 larger than the paint we are using. If it starts on one side of the barrel and ricochets down the barrel and hits using simple reflection only 2 times on the way down the barrel, It will exit the barrel at an angle of 0.143 degrees. It will show the exact shot pattern deviation in the above graphs.

There are a couple of things you are assuming that are incorrect. First, that the paintball will ricochet the same each time and therefore will ricochet at the point that gives the max angle. It won't. The second problem is that for your numbers to be correct the paintball must travel in a straight line. I think we can all agree that it does not come even close. The problem is that the minor deviations are lost in the 2Gs worth of random lateral force knocking the paintball around as it travels down range.

BTW, this also follows my own personal observations. Anytime I let someone use my stock emag barrel they ALWAYS comment on how accurate it is. The bore on that thing is very large. :D



The US Naval Ordinances and Gun Barrel Construction guide where it talks about old cannons it states "There were other reasons, too, for the inaccuracy of early gunnery. ...close clearances would have made loading impossible, the shot was a fairly loose fit.

I think you would find a paintball marker very accurate compared to one of those. When they say loose fit it is many orders of magnitude different from what we are calling a loose fit.



I have also seen many barrel reviews and have seen many shot dispersals. Generally 6 inches is the best it can get but I would rather have 6 inches than 12 inches.

So would I! However, there just isn't anything that can make that big of a difference.



I hope to convince you that you are wrong on this.

That's why I'm posting. Hoping to share knowledge. I have learned a lot from this forum. I hope to continue that. :D

Respectively,
Hitech

[Wat]

I would presume that shot dispersion is also effected by the variance in the paint and varience in the air. Remember, a paintball is very light, small variances in wind, air temp, density, birds farting nearby will have a noticable effect on your shot pattern. Even the orientation of the seam will make a big difference.

You could have a million bucks but you still couldn't build a wiffle ball launcher that would hit the same spot consistantly at 50 yards.