Accuracy in Paintball - Part One

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Accuracy in paintball

In paintball, no matter what kind you play, it all comes down to getting your ball on target.

You hear about this all the time, Paintballs are not accurate because they are round.  They are not real bullets and the barrels cannot be effectively rifled so they cannot be accurate.  Is this true?  Yes…and no. If someone defines accuracy as being on par with a regular firearm where you can hit a man sized target from 400 yards away and have it be effective then no.  If you redefine just what is accuracy then the answer doesn’t become so simple though.  So can paintballs be “accurate”?

We are going to make some assumptions here.  We will assume that your equipment and the paintballs you shoot are clean from paint and dirt.  Both of these items will make ANY marker highly inaccurate. So if you break paint in your barrel, hopper, pod, or get dirt in your paint these problems have to be addressed in order to have an accurate marker.   

What is accuracy?

Here’s where things can get a little fuzzy, defining accuracy.  First let’s look at what we are dealing with.  We have a round projectile being fired out of a smooth (usually) bore barrel at a low velocity using a gas pressure to provide acceleration.  That is the firing of a paintball in simplest terms.

So under these conditions what is “Accuracy”?  Accuracy is inherently tied into range.  The maximum effective range of the projectile coupled with the probability of the projectile striking the target at that range determines how “accurate” that device is.  Accuracy is also a relative concept.  Like we mentioned before, if you compare a paintball marker to say a 30-30 Winchester rifle the rifle will outperform the marker every single time.  However, we don’t use Winchester rifles in paintball so it is an unfair comparison. 

So keeping those two concepts in mind, let’s look at paintball markers and see what factors need to be considered when talking about accuracy. 

"Long range" in paintball is a relative term. With the limited range of your average paintball marker, engagements such as this one on an airball field usually happen at ranges of under 100 feet. Photo courtesy of Paintball Photography.

Effective RangeThe effective range of a paintball marker is the maximum range at which a paintball will break when fired at or under the maximum allowable velocity for that field.  So what is that distance? It is anywhere from 10-200 feet.  Pretty broad range, huh?  You see, paintballs don’t always break when they hit their target.  What part of the opposing player they hit, the material or items the paintball strikes, the angle with which the ball is moving in relation to the area of impact, the temperature, and the condition of the paintball shell all determine if a ball will break on target or not.  That’s not even taking into account any variance in the velocity the projectile is traveling when it leaves the barrel. Thus not every “hit” will result in an elimination. 

So let’s set some constants in order to help define a paintball’s effective range.  It is safe to say that a paintball hit anywhere on a target less than 50 feet away will break 90% of the time.  I’d also say that a hit anywhere on a target less than 100 feet away will break 70% of the time.  Obviously hits on “stiff” components such as pods, guns, hoppers, lenses and the like will have a higher break probability than those hitting softer parts of a persons body like thighs, torsos or the upper arms.  If striking one of these areas the chances of breaking a ball on them up to 200 feet is still pretty good.

So let’s set the effective range of a paintball marker to about 100 feet.  Again, this number is just based on my own personal experience and not every ball will break at 100 feet but chances are still pretty good at achieving an elimination at this range. 

Realistic Comparisons – So what do we compare?  Well, it’s simple really…other paintball markers.  We’ve already accepted the fact we’re not going to hit someone in the head from 100 yards away with a paintball marker with anything other than luck.  All we can compare the accuracy of one marker too is the accuracy of another marker. Thus when we talk about accuracy it’s all relative to what other markers can do.

So for us in the paintball world, accuracy is the probability of striking a target up to 100 feet away in comparison to other paintball markers.

Physics and paintball specific accuracy items

So now that we have a definition on what accuracy is, what affects it when it comes to paintball?  The list is actually pretty big and can be broken down into two categories: General Physics and Items Particular to Paintball.

General Physics:

  • High speed camera series showing the acceleration of a partical of snow because of gravity.
    Gravity – Yes, that magical force that dropped an apple on Newton’s head.  Everything is affected by gravity.  If I remember my High School science class well enough, gravity, on Earth, is a force that accelerates objects at a rate of 9 meters per second.  That means that if you fire a paintball on a level trajectory that after one second of being in the air it will be traveling TOWARDS THE GROUND at 9 meters per second.  After two seconds it will be traveling towards the ground at 18 meters per second.  After three seconds…well, you get the idea.

  • Friction – When you have two surfaces rub against one another they create a force between them called friction.  Pretty simple concept.  While we deal with friction when we talk about drag (see below) we also need to think about the friction between the paintball and the barrel when we are discussing paintball. 

  • Drag – Drag is a force caused by the paintball moving through the air that pushes against it as well as the friction caused by the air moving over the paintball’s surface.  Drag causes the paintball to slow down.  The paintball may leave the barrel at 300 feet per second (fps) but as it travels through the air it will decelerate because of drag.  Also, drag is not a linear force.  The faster an object moves through the air the greater amount of drag is produced.

  • Lift – Lift is the force that can counteract gravity.  Planes use lift to fly.  If the amount of lift on an object is greater than the force of gravity pulling down on it, the object will rise in relation to the Earth’s surface.  If the amount of lift is less than the force of gravity but still greater than zero lift, the object will still fall at an accelerative rate but that rate will be less than the normal 9 meters per second.

  • Thrust – Thrust is what overcomes Drag.  We don’t deal with thrust really when it comes to paintball but the concept is still important to keep in mind.  Thrust would be like the propeller on a plane pulling it through the air against drag.  Because there is nothing on a paintball providing thrust, drag is never overcome and thus the paintball will always slow down after being fired. 

  • Image showing the movement of air around a paintball in flight and the turbulance created by its wake.
    Aerodynamics – This is something that will pertain to paintball.  The better Aerodynamics an object has the less drag is produced by it moving through the air.  Thus if two objects are begin traveling at the same velocity the object that is more efficient aerodynamically will travel further because it will have less drag trying to slow it down.  However, without a means of producing thrust, even the most aerodynamic projectile will eventually be overcome by drag and stop moving.

  • Inertia – Another gem from Newton.  He had three laws of motion and while they are all important the one that concerns us with paintball are his first two.  The first law states that “An object at rest tends to stay at rest unless acted on by an outside force” and “An object in motion will stay in motion unless acted on by an opposing outside force.”  This is called the law of inertia. There are two ways in which inertia acts on a paintball.  When the ball leaves the barrel, it is both in motion AND at rest.  How’s that you say?  Well, remember it is moving in THREE different axes.  The first axis is the ball moving away from the barrel.  This is measured in feet per second.  So it is moving at 285 feet per second.  Drag is the opposing outside force and is working to return the paintball to an “at rest” state. But there are two more axes to consider.  The other is the relation of the ball to the ground.  When the ball leaves the barrel, and assuming the barrel is level, the ball is not accelerating towards the ground yet.  Gravity acts upon the ball shortly after it leaves the barrel and becomes the outside force causing the ball to go start moving towards the ground from it’s at rest state.  The third axis of motion is the movement of the ball either left or right from where the barrel is pointing towards.  While other factors will affect this (which we will get into later) the most obvious would be if you were shooting into a crosswind.  The wind would start the ball moving away from the direction it was originally heading.  It is important to keep in mind these three axes and how inertia acts upon the ball in all three when dealing with accuracy. The weight of the ball will also affect its inertia.  The heavier the ball is, the more force it will take to change its state.  This means a heavier ball will decelerate less over the same length of time and be affected less by wind than a ball that weighs less.  However, the weight differences between paintballs are minor and usually plays very little role in how accurate the shot is.

  • Acceleration – The other Newton Law of Motion we have to worry about is his second law.  It states that a body will accelerate in the opposite direction at a proportionate amount in relation to how much force is applied opposite that direction. This is where gas pressure comes into play when it comes to paintball markers.  The greater the pressure and amount of gas that is put behind the ball, the greater that ball will accelerate and the faster it will be accelerated to.  This is important to understand because the faster the ball accelerates to then the faster it will leave the barrel.  The faster it leaves the barrel the greater the inertia and the greater the inertia the longer it will take drag to slow it down.

Quite a bit to digest, I understand.  However to truly understand accuracy you have to understand how all these things work. 

Items particular to paintball:

  • Paintballs – Since ultimately it is the paintball itself that we are trying to get to hit the target, the attributes of the paintball are critical to how close to our target we hit. 

  • Barrels – One important item that helps deliver our projectiles on target is the barrel.  From length, to coating, to shape and how the barrel interacts with the paint barrels are critical to the accuracy equation.

  • Air Source – The gas that propels the paintball also plays a vital role in how accurate a paintball marker is.  Pressure and volume are both critical items that will determine whether or not our markers are accurate or not.

  • Marker design – For the most part, the design of the marker plays very little role on how accurate it is outside of the air source used, barrel, and paint.  However, there are a couple items that can help a marker be more accurate.  They are how easy is it for the marker to prevent paint chops and the affects of recoil on accuracy after the initial shot under multiple shot situations.

Now there are other things that we could include in here like sights but really those are tools that assist the shooter taking advantage of the accuracy of his or her marker. A sight, in and of itself, does not make a marker more or less accurate.  Remember, we are just talking about the accuracy of the marker itself, not how capable the shooter is of aiming the marker correctly.

The process of firing a paintball

Most understand how a paintball gun actually fires a paintball but I be you never really thought about the whole process and broke it down bit by bit.  So let’s quickly go over exactly what is going on from the time the air starts moving until the paintball goes splat!

Animation showing the firing process of an Automag. Some steps in this process affect your marker's accuracy while others do not. Animation courtesy's Marker Animation page.

When you pull the trigger you set off a series of events that culminate with a specific volume of gas moving through a valve at a specific rate and pressure.  This gas is directed against the ball by your marker’s bolt.  This gas is of a greater pressure than the air that is in front of your ball and the friction of the ball against the barrel. Because of this, the gas begins to accelerate your ball down your barrel.  However, as the ball moves further down the barrel the pressure of the gas begins to decrease because it is trying to fill an ever increasing area (the area between the bolt and the back of the ball).  The force of this gas through the length of the barrel, minus the air resistance in front of the ball and the ever increasing amount of friction between the ball and barrel, result in the ball leaving the barrel at a given speed.  This speed can be measured in Feet Per Second by a Chronograph. 

Once the paintball leaves the barrel it is acted on by a number of different forces.  The first is Drag created by the air the paintball is moving through.  The second is gravity which begins to accelerate the paintball towards Earth.  The third is wind that attempts to push the paintball off course. These three forces apply to every paintball.  Other forces that will affect the paintball are its weight, its shape, and its rotation.

Drag will slow the paintball down giving it less energy on impact the further away from the paintball marker that fired it that it travels. Gravity will eventually bring it into contact with the ground if it does not strike anything else before reaching the ground. Wind and rotational forces will cause arbitrary course deviations based upon type, strength and direction. 

I know, seems pretty straight forward right?  Well realize that there are some things here you have control over and some things you don’t. The paint used, the barrel used, the air source used and the angle at which the ball leaves the paintball marker in relation to the ground and wind direction are all things you can control.  Gravity, drag, and wind are things you cannot control.  You may think why am I mentioning this as it seems so obvious?  The reason I mention is because many times people get hung up on things they have no control over instead of looking at the things they can control.

End Part One

Well, that wraps up part one. Stay tuned shortly for part two where we talk about the different forces that affect the flight of a paintball.

Good luck and remember, it is all about having fun!

- Robotech

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