Ok.. some hole in the arguements used against Tyger's explanations..
1. Paintballs are liquid inside, true.. but what people fail to take into consideration is the viscosity, or thickness of that fluid. Bill Mills actually did a test and used it as an arguement against Tom Kaye's "rifling does nothing" article. He put a paintball in a motorized mount similar to how a lathe works and spun it for days. His purpose was to try and get the pigment in the fill to mix evenly, as the paint was old and the pigment had settled. The problem he had was that the fill was so thick it spun with the paintball and the pigment would not remix, as you would think would happen if the fill was less viscous.
The fill in 90% of todays paint is so thick that it bonds to the shells and spins with the shell, in essence acting like a solid. I think wild streak is the only stuff I've seen that is a true "liquid" fill anymore. It breaks open and runs like orange soda.
The "EGG" analogy... again.. paint fill is actually MUCH thicker than the yolk, or the whites of an egg.
some forms of rifling are more effective than others. this is where the arguements about range come into play. (now for the unintelligble technical explanation with a confusing analogy!)
Air pressure affects all surfaces of a sphere equally, except during motion.
there are TWO types of drag that effect any object traveling through the air. Wind resistance, and pressure drag. for a sphere, the wind resistance is considered negligible since all surfaces are considered even.
Imagine a globe in a stand turned on it's side. now spin the globe. if it were a paintball, the air pressure would most effect along the equator, or in a vertical path. this is what generates the magnus effect for flatlines. If you notice though, at the poles where the stand holds the globe, the rate of rotation is much slower. this results in unbalanced pressure, and pressure drag on the surface of the paintball. the top of the paintball, which is rotating with the direction of the air, has the lowest pressure and minimal drag, while the sides have neutral pressure and normal drag, and the bottom has the greatest pressure and higher pressure drag.
this is also why some people notice a marginal accuracy with the flatline. at distance, when the paintball begins losing forward momentum, any pressure differences on the sides 90░ to the direction of rotation will have higher impact on direction aka gyroscopic precession.
now take that same globe on its side and spin it. only this time, the paintball-globe is traveling in line with poles, and the rotation is 90░ to direction of travel. since all the air is being directed evenly across the surface, the rotation is affecting the air pressure evenly across all the surfaces and is deflected, putting kind of a spiral on the air currents. this is known as the Coriolis force. As the air currents reconverge on the back side of the paintball, the currents and pressure have lower imbalances and smoother interaction, which reduces pressure drag altogether, while still centering it behind the paintball. you dont end up with as much distance as from the magnus effect, but you do have some improved distance and accuracy due to the decrease in pressure drag. the design of how spiraled rifling is achieved also has great effect on how much and how effective the amount of coriolis force is applied to the paintball.
straight rifling has a similar effect, only through opposite means. Straight rifling prevents any rotation of the paintball, which allows for air pressure and currents to naturally stabilize over the surface during flight, instead of inducing the stability, which has the greatest effect for point to point accuracy. It also has the greatest detriment. If any part of the paintball surface is uneven or has a dimple, it creates a very high imbalance of pressure and flow at that one point which will cause a sudden high rotation and throw the paint in that direction, like throwing a curveball, only much more drastic.
With a smoothbore barrel, the air pressure, and friction with the inside of the barrel will cause some minor uncontrolled rotation on various axis. this causes a random differential in where the pressure drag is generated on each paintball and causes such a wide spread of where paint goes with each shot.
Having a good paint to bore match has the greatest effect on velocity control, not accuracy, as most are inclined to believe. the highest level of accuracy has to be obtained through a balance of bore size and length of your barrel, because almost ALL barrels increase in bore size from the control bore to the muzzle.
As for the rifling 'cutting' into a paintball to be of effectiveness. this is not true. what people fail to take into consideration is the material of the shell, and how the rifling is achieved. Rifling is cut into the BARREL, not the other way around. with the pressure of compressed air, or even co2, the shell of a paintball is deformed to fit the barrel surface, essentially molding the shell to the rifling. the only reason that firearm rifling is made to cut into the surface of the bullet is due to the extremely high velocities.
Snyper06: The crimping you are refering to in the jacket of a bullet is caused by the manufacturing process. it has nothing to do with rifling. Modern rifling methods were invented by the french prior to the 1800's, when there were no metal jacketed bullets. round musket balls were used. The US used rifles against the British towards the end of the revolutionary war. Rifling insome form or another has been used in firearms since the 1540's. The ammo was still round lead balls. the actual pointed shape of the modern bullet did not come into wide use until the Minie bullet was developed in the 1840's
This post has been edited by sartek: 01 May 2006 - 03:06 AM