This is a somewhat lengthy article, but I want to dispel some myths circulating in the paintball community.
Ballistics is the science of how an object acts when propelled through the air. As applied to paintball, there are a few firearms ballistics rules that apply, but only a few. To apply firearms ballistics as a blanket, over paintball ballistics is totally inaccurate.
Allow me to qualify what I'm saying with a little bit about my background. I am a qualified sniper, I am also qualified as a firearms instructor (foreign and domestic). I am also a skeet shooter, a plinker and have dabbled in practical competitive shooting. To shoot a firearm well, you have to understand ballistics. All of this to say that I know what I'm talking about, when it comes to firearms.
I have been playing since 1984. I have shot more types of markers than I can remember. I have completed extensive research into what a paintball does when it is fired. All of this to say that I know what I'm talking about, when it comes to markers. (Incidentally, I'm a better shot with firearms than I am with markers, which may go to prove my point further, but it's a poor workman that blames his tools.)
However, there are firearms ballistics fundamentals that apply. Trajectory, projectile shape, barrel length, barrel material, projectile outer diameter, barrel inner diameter, barrel configuration and the surrounding environment.
What do not apply are velocity, the projectile make-up, the projector type (marker), projectile spin, and barrel material.
Let's look at each one.
While the trajectories of bullets and paintballs are similar (in the fact that they arc) they differ in the fact that the ranges are shorter for paintball and the velocities are lower. The lower the velocity, the higher the trajectory has to be in order for the ball to travel the distance you want it to. The reason for this is your old friend gravity.
Gravity is a product of time, not distance, and therefore the trajectory has to have a higher arc if the projectile is travelling slowly. Like an arrow.
A round projectile is the most ballistically inefficient shape. That is why firearms have not shot round balls for a few hundred years. The conical shape is the best way to go due to the fact there is less surface area at the front of the projectile and this reduces air resistance. (I'll get to spin later on).
In paintball the best barrel material found so far is brass. There are other surfaces which are smoother, but as the paintball travels the barrel, it leave minute amounts of gelatin behind. Brass doesn't seem to pick this up as much as other materials.
Whatever material you use, it must be as smooth as possible to reduce the friction between the ball's shell and the barrel's surface. This is called the drag coefficient and it is more important in paintball than in firearms, due to the lower velocities in paintball ballistics.
The outer diameter of the projectile is important because it directly interfaces with the inner diameter of the barrel. In paintball we have the advantage over this problem as compared to firearms owners. We can easily change barrels and do not have to worry about the outer diameter as much when producing paintballs, as they have to do will bullets.
Which brings us to . . .
Barrel diameters in firearms are very standardized because of the standardized projectiles. Paintballs are close to being standardized, but there are too many variables to get something as consistent as bullet diameters. This is where interchangeable barrels come into their own. You can fit the barrel to the projectile.
This is important because if the barrel is too large, the ball will not seal the barrel when fired. If it is too small, it will increase the drag coefficient and reduce velocity and performance.
However, many people get hung up on specs that are measured in what are known in math as "insignificant digits". A plus or minus of .002" around .690" is virtually impossible to tell with ANY brand of paint. It takes a good $600 Mititoyo bore gauge to see the difference. When the balls can vary by .02" from around the seam to perpendicular to it -- maybe we are getting a little foolish trying to specify to within .0005" on barrel inner diameter.
I am talking about porting, the little holes in the barrel. (I told you I'd get to it.) Remember when I talked about barrel length? I has said that some believe that atmospheric pressure stacks up in front of the ball. This is true. I said that the ports help alleviate this. This is true. But porting does much more than that. If your valve is letting out too much gas then the excess gas is causing turbulence behind the ball and may start it spinning. This is a bad thing (and I'll get to it later -- one thing at a time). The porting allows the gas to dissipate gradually and not blow out the muzzle with the paintball. This blasting of extra gas at the muzzle is known as "blow-by". This greatly decreases ball stability. The porting allows the gas to leave and the barrel holds the ball in a relatively stable condition.
This "extra gas" is why when you compare two markers from the same manufacturer using a ported barrel, one shows improvement and another may not. It is your VALVE that is the culprit, not the barrel. Now a valve job has to be done by a qualified airsmith, it's a lot easier just to buy a ported barrel.
A muzzle brake on a marker works the same way. On a firearm the muzzle brake helps to control recoil (of which there is none on a marker). We call it a muzzle brake because it looks like one, not because of what it does. (Note the spelling: because if you have a muzzle BREAK, you better get it fixed.)
Weather effects ballistics. Weather, in our sport, effects the actual projectile as well. Humidity, wind, and temperature effect paintballs far more easily than bullets.
Here is the real clincher. Apart from the type of projectile we're firing, velocity is the key factor in why firearms ballistics doesn't completely apply. Even the lowest velocity bullet is still a lot faster than a paintball. Due to the fact that the velocity is so low many firearms ballistics rules do not apply.
The great thing here is that what does apply is ideal velocity. Depending on projectile weight, barrel length and other factors, there is an ideal velocity for your marker. Chrono at a safe velocity and shoot about 20 balls at a large target. Now adjust your velocity and do it again. Is there a difference in how close together the balls hit? I have found that each marker has it's own ideal velocity where the balls hit the target closer together than at other velocities. This ideal velocity must be determined each time you play because the weather is different each time, as is the paint. I have found the fluctuations are around 5 to 10 feet per second, so it is a minor (and not very time consuming) adjustment.
Here is where paintball ballistics has it's most severe limitations. They taught us in sniper training that the rifle is only as good as the projectile it fires. That's why snipers use hyper-accurate ammunition called "match-ammunition". To date, there are no "match-balls". It would be impossible, anyhow.
The machines that are used to make paintballs are set by volume, not size. It is almost impossible to consistently maintain ball diameters from production run to production run.. That's why Brand X worked well last month and rolls out your barrel this month. Making paintballs is more of an art than a science.
We also have to take into account that the ball has a seam. This is a bad thing. The seam catches the air (like a baseball seam is supposed to do) and will curve and spiral. I'm sure you've seen that.
Add to all of this the liquid fill of the paintball. That fill moves around in the ball, and an air gap makes it much worse. When the fill moves, so does the ball.
On top of this, firearms manufacturers don't have to worry about the firearm breaking the bullet. This is a major concern for marker manufacturers. The easiest solution is the venturi bolt. Like every other technological marvel in paintball, there are trade-offs.
Venturi bolts tend to create even more turbulence. Instead of one hole to create the little whirlpool of turbulence, now you have a half a dozen doing the same thing. If you have this "extra gas" problem already the venturi bolt will only make it worse. If your marker is not routinely breaking balls at the bolt face (indicated by shell and paint on the bolt face) you do not require a venturi bolt.
The marker is not a precision shooting device. (Notice I didn't say "accurate"? Precision is the marker's ability to shoot consistently and put the balls in the same place--say when clamped down in a shooting vice. Accuracy is the product of the shooter's ability to stabilize the marker when shooting.) A marker can be made to be as precise as humanly possible, but no where near a firearm. Take it from someone who has shot at a six inch bullseye at 1000 yards with a highly tuned sniper rifle, markers suck for preciseness.
You see there are several more working parts on a marker than there is on a comparable firearm. They each share parts like sears, triggers, barrels, bolts and hammers. In a marker we also have valves, and other pressure regulatory systems. To make matters worse, unlike firearms, markers also have a power source that diminishes with each shot.
PROJECTILE SPIN.
The paintball has a seam and a liquid fill. Spinning the paintball causes the seam to catch th air and start its curve. Spinning the liquid destabilizes the ball. Think of a water balloon. A paintball acts in the same manner, wobbling and changing it's shape as the flexible shell and the liquid react to the spin.
To prove the point that spin is bad allow me to sight a very common example of spin. When you have paint in your barrel, it will cause the the shell of the ball to slip, usually beginning the spinning process. This is why the balls corkscrew in the air. They are spinning.
Spinning is a bad thing. The ported barrels actually help stop the ball from spinning, thus stabilizing it (just not when they are wet with paint, that's what squeegees are for). Not the other way around. The porting is usually in a spiral pattern because it looks more pleasing to the eye.
Confused? Well you should be. Comparing firearms ballistics and paintball ballistics will only lead to more. Understanding the differences will help you understand why you just can't seem to get the balls to do what you want them to. It will also help you separate fact from fiction when choosing aftermarket accessories.
But then again, you get what you pay for. It only costs a few cents to make a paintball, you're getting you money's worth.
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