Bore Sizing Tech Tip #2
By popular request I will divulge the inner secrets of bore/paint match ( is was 101 degrees out in the field today so I came in early)
Does having a good paint barrel match improve your accuracy??? YES. How does it do it? Very simple, if your gun shoots with a consistent velocity the paintballs will tend to follow the same arc, thereby improving accuracy. It technically is making your gun more consistent which is a better term than accuracy.
Historically there were many theories about paintball barrel matches. First there was the Tippman theory where they used a very large bore barrel and claimed that the air escaped evenly around the ball and it floated down the barrel without touching anything. They claimed this was the "air bearing effect". Next there was the tight barrel theory that said if the ball seals all the way around the shot will be more accurate. Actual testing has proven both these theories false.
Why match paint to barrel? Going back in time the paintballs were much more inconsistent than they are now, in fact now they are really, REALLY round and half the price. Players found that their consistency/accuracy improved when they used certain size barrels. Unfortunately paint is constantly changing size and this requires different barrel id's to work well.
The technique used to research paint/barrel match is simple and doable by anyone. Testing is performed by blowing a thin powder down the barrel to coat the inside. We used to use Desenex Foot Powder that sprayed on dry. Todays Desenex is a different formulation and doesn't make a powder. Once you have coated the barrel you dry fire the gun once to clear out any extra powder. Lastly shoot one paintball out the gun and inspect the inside of the barrel. The powder will be stripped away everywhere the ball touched. This allows you to see exactly what happened to the ball down the barrel.
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. Tighter barrels that were too long were found to slow the balls down due to this friction. In other words, when you cut these barrels down, velocity went up. Remember the 8-10" acceleration distance, these barrels were 14" long and unported.
The best paint barrel match left two 1/8" wide streaks opposite each other down the barrel. The widest part of a paintball is usually the seam which is also called the equator. With a proper size match only the balls equator touches the barrel snugly on two points. The equator tends not to align itself so the entire seam touches the barrel hence you only get two points touching. So what is happening here that makes this so desirable? We all know paintballs vary in size, this means that there will be slightly more or less friction on the ball depending on how tightly it fits in the barrel. If you use too tight a bore that touches the ball all around, trying to squeeze a bigger ball in greatly increases the friction and changes your velocity. By having the barrel sized to only touch two points, bigger or smaller balls only increase the contact patch a small amount and this gives you better shot to shot CONSISTENCY. To large a bore solves the friction problem but you get back to the ricochet effect.
So this is the story behind proper paint/barrel match. Many of you have commented that the stock barrels seem to work about as good as custom barrels. This is because todays paint is so much more consistent than 10 years ago that the difference between barrels is much diminished. Even the biggest to the smallest barrels don't product that much difference in accuracy IF YOU ONLY COUNT THE SHOTS AT THE SAME VELOCITY. So there you have it, I should mention these studies were done in the early to mid nineties, we have not done any testing lately on two piece barrels etc.