WHAT MAKES A BARREL
ACCURATE?
In response to your many questions, here are some of the factors that contribute to barrel accuracy and reliability.
BARREL CONSTRUCTION
Let's look at the manufacture of paintball barrels, starting with the selection of materials, then smooth-bore finish vs. rifling, bore diameter, length porting, and muzzle break. Then we need to see the part played by the ammo itself.
IDEAL MATERIAL
Based upon 17 years and hundreds of thousands of paintball barrels we have made, without doubt, aluminum has proven to be the best material. It is lightweight, fast machining, and it finishes very well. Everyone understands that friction is to be avoided as much as possible. When anodized aluminum is compared to other materials, the coefficient of friction is about ten times less than in stainless steel, brass, composites, or other metals.
Stainless-steel barrels would appear to be very durable. Let's compare stainless steel with anodized aluminum. Anodizing is forming a layer of aluminum oxide on the surface of the aluminum barrel, both internally and externally.
Known as corundum or emery, naturally occurring crystalline forms of aluminum oxide have been used as abrasives for grinding and polishing of the hardest elements known to man. Aluminum oxide is rated Number 9, second only to diamonds on the universally known Moh's hardness scale. There are no other barrel materials with greater hardness and resistance to wear than anodized aluminum barrels, including stainless steel, which is rated between 7 and 8. If someone tells you that a gelatin-capsule paintball can wear out your aluminum barrel, say that you have a bridge for sale.
RIFLING
Barrel engineering began with the cannon, the first weapon to fire round, steel balls. Because the cannonball was spinning in the barrel and as it left the barrel, accuracy occurred only at very close range, normally a few hundred feet. Cannon makers experimented to reduce spin, and, in 1863, a man named Steele secured a patent for ballistic rifling, the first of various patents in this area. His patent consisted of four linear, square grooves, cut on the interior bore of a cannon. This concept immediately improved accuracy and distance. The grooves' edges actually cut into the steel ball, keeping its spin at a minimum after it exited the barrel.
Skipping to the end of the 20th Century, we get into barrel engineering for paintball markers, which also fire round projectiles. At CMI, we spent over three years in research and development, applying principles of linear rifling to paintball barrels, and were awarded a patent for our TRU-FLIGHT Barrel process, Patent #6453593, to reduce spin, thereby increasing accuracy. For properly round paintballs, these barrels eliminate spin and achieve maximum accuracy.
SPINNING VS. NO SPIN
Another paintball equipment manufacturer, Tippmann, produces a barrel which, instead of eliminating spin, exploits the spinning effect of the ball in the barrel. Creating a gyroscopic effect, that process makes for greater distance, but accuracy occurs only if the marker is held TDC (top dead center).
MUZZLE BREAK
When a paintball is not perfectly round, and spins as it leaves the bore of the barrel, it creates a turbulence known as eddy currents. Aggravating this problem is the air that is expanding in the barrel to propel the paintball, as well as the clash of this air with the still atmosphere the ball enters as it leaves the barrel. These eddy currents are a major case of balls curving and hooking. To help reduce these currents, the paintball barrel should have, in addition to linear rifling, a proper muzzle break.
The muzzle break's most important job is to reduce or eliminate the expanding gases that push the paintball, so as not to create eddy currents after the ball leaves the barrel.
By allowing air to escape just before the ball exits the barrel, the muzzle break reduces the shock and recoil of the projectile and expanding gases as they exit the bore, therefore reducing the possibility that the ball will have an erratic trajectory.
Simple holes drilled in the muzzle break or front of the barrel are not an efficient substitute for a properly designed muzzle break, since paintballs are not subject to the high pressure that occurs with the explosion of gunpowder.
A patent was also awarded to CMI for the design of its Turbulence Scavenger Muzzle Break, Patent #6276354B1, used exclusively in our barrels. This design incorporates the Venturi principle. The Venturi effect used in our muzzle break accelerates the exiting gases via the slots in the muzzle break, thereby reducing the gas volume that would normally exit via the bore of the barrel. This reduction of gases also minimizes disturbance to the paintball's flight. A well designed muzzle break will increase dramatically the accuracy of a paintball barrel.
PORTING
FOR QUIET PERFORMANCE:
QUIET BARRELS, THE ULTIMATE IN STEALTH
Years of research and development culminated in CMI's Quiet Barrel. The achievement of maximum noise reduction was reached by the design of the most effective location, number, and diameter of the porting holes. CMI's porting reduced the noise made by a paint marker from a high average of 109 decibels (equal to a scream) to a low average 70 decibels (normal tone of conversation). This noise reduction helps conceal the shooter's position for GREATER STEALTH.
PAINTBALL QUALITY
By now, you should understand that round balls present many more problems than bullet-shaped projectiles in achieving accuracy.
Linear rifling produces ideal accuracy with perfectly uniform paintballs. Unfortunately, paintballs are not uniform, and so our barrels are not always able to reduce or stop spinning.
Most of the problems with paintballs have to do primarily with roundness, then seam quality, humidity, and density. Some of these problems originate in the manufacturing of the paintballs; others are effects of weather or storage conditions. Very out-of-round paintballs, paintballs with poor seam quality, old balls that have been allowed to swell from humidity or that are not uniformly dense will not be accurate, no matter what corrections are attempted.
The pigments used to color paintball fills are as varied as the color selection itself. When paintballs sit warehoused for long periods of time after manufacturing, the pigments used for coloring the fill will precipitate (separate from solution). Some pigments precipitate faster than others. This pigment will settle at the bottom of the ball. When the ball is shot out of the barrel, and it spins, the uneven weight distribution will cause the paintball to fly very erratically. TAKE THIS OLD PAINT BACK TO THE DEALER.
Paintballs are supposed to be manufactured for 68-caliber barrels. Some manufacturers make balls of larger diameter, some smaller. Paintball players should use only the paintballs that are the closest in diameter to .68 calibers.
Remember, when a paintball is much larger than .68 calibers, its size will create more drag in its flight, which will reduce distance. On the other hand, when a paintball is smaller than .68 calibers, it will not have the mass for the proper muzzle velocity of a 68-caliber barrel.
The idea is to select a barrel size that performs well with the majority of paintball brands.
CMI'S DUAL BORE
In order to accommodate the variations in 68-caliber paintballs, most barrels are made to .685 calibers. CMI has developed a dual barrel bore of .688 through the barrel and .6925 in the rifled grooving. These dimensions will accept most of the paintballs produced.
BARREL LENGTH
In theory, and under ideal conditions, paintballs will have sufficient acceleration and adequate momentum to attain 300 feet per second with an 8- to 10-inch barrel. However, since we do not have ideal conditions to maintain consistent acceleration and trajectory, we have to compensate by using a longer barrel to improve target efficiency. A 9- to 12-inch barrel is suitable for close arena games. For longer distances, a longer barrel is needed to overcome wind, humidity, and temperature. These obstacles can be reduced to more acceptable levels with the choice of a longer barrel, such as a 14- to 16-inch or even a 21-inch barrel.
Your marker, your style of play, the paintballs you are using, the weather, and field terrain are all to be considered. Accuracy will be your reward for proper selection of barrel length.
SOME CAUSES OF BREAKING BALLS
1. The pinched ball is not completely in place in the breech of the marker (too fast a trigger).
2. There are tiny nicks on the leading edge of the barrel where it attaches to the marker.
3. Seams on the paintballs are of poor quality.
4. The paintball is old so that the gelatin capsule has lost its flexibility.
5. Paintballs being used are much larger than the bore of the barrel.
6. There are spikes in pressure whereby a ball may be distorted and the seams fail in the barrel.
If you want to see an amazing improvement in the performance of a paintball barrel, size your paintballs for a consistent dimension. Be sure to use a gauge that has at least ½-inch thickness, so that you can rotate the balls on their axes while inside the gauge to check the roundness of the paintballs.
And as you become technologically more proficient, here are some words that you should know:
ACCELERATION - The rate at which the velocity of a moving body increases
BALLISTICS - The science dealing with the motion and impact of projectiles such as bullets, rockets, bombs, and paintballs
FRICTION - The resistance to motion of two moving objects or surfaces that touch
INERTIA - The tendency of matter to remain at rest if at rest, or if moving, to keep moving in the same direction, unless affected by some outside force
KINETIC ENERGY- The energy possessed by a body as a result of its velocity
MOMENTUM - The force with which a body moves against resistance
MUZZLE VELOCITY- The speed of a projectile, such as a paintball, as it leaves the muzzle of a firearm or a paintball marker
RIFLING - In the case of firearms, the cutting of spiral grooves on the inside of a gun barrel to make the projectile spin.
In the case of CMI paintball barrels, the cutting of linear grooves on the inside of the barrel to prevent spinning
TRAJECTORY - The path of a projectile from the time it leaves the muzzle of a gun
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Joseph C. Dillon
President, CMI International LLC
Copyright © 2005 Calmedia. All rights
reserved.