TAC-8 Accuracy modifications

 Status: Abandoned

Although this project was a lot of fun, I have completely abandoned it for an off-the-shelf solution. For once, a manufacture listened to what we the users wanted. Ok, well, in this case, what I wanted. To make a short story long, the following data simply supports the fact that most of what effects accuracy of your paint ball gun has to do with the paint itself.

IF YOU WANT TO BE A SNIPER on the paint ball field. Ignore all of the hype, simply go here:

www.tiberiusarms.com

and get yourself a T9 or a T4 and some First Strike paint balls. I prefer the T9, but thats just me. You may want the higher capacity 14 round mags of the T4. Its quite the experience to go out on the field and after the first game, the people on the opposing team practically kill themselves diving for cover when they see you.

I know this isn't robot related, well at lest not yet!!! Anyways, this new project is an attempt to fabricate an extremely accurate (accurate as possible in paintball terms) paintball sniper marker.

When most of us think of a sniper, we think of a squared away jarhead wearing a ghillie suit quietly sneaking about the jungle occasionally picking off one of the enemy from very long distance. However, when you try to apply this concept to paintball most of what makes a sniper a sniper is lost or nullified.

The Battle Field - Unfortunately, with regards to playing paintball, I live on the west coast where undeveloped land either does not exist or is protected in one way or another. In other words you can't just grab your gear and start playing paintball in the woods without begin arrested by the police or having a forest ranger put a rather large knot on the top of your head, then arresting you. The only alternative is to use a pay-per-play field, of which there are only a few within driving distance. These pay-per-play fields typically have a multitude of battle fields with various themes, urban, jungle, desert etc. Most of which are smaller than a football field.

Due to the small size of the battle filed, the snipers greatest weapon, stealth and concealment are almost completely negated making camouflage and or the use of a ghillie suit worthless.

The Weapons of War - I started playing paintball 20 years ago with pump actuated markers with 10 round magazines and a Co2 cartridge. You had to get up close and personal with your victim, lay in wait and take a well aimed shot, usually missing. Things are a lot different today; everyone is running around with portable gatling guns with a zillion round capacity, spraying paintballs all over the place and still not hitting much of anything. I find little, if any enjoyment shooting 200 paintballs in the course of a game to end up with the same kill ratios as when I was using an old pump marker.

In an effort to bring back what I found enjoyable in playing paintball and still remain competitive, a new paintball gun must be developed………..

Battle Tactics - Rather than pretending I'm an employee at Maaco and spray painting the battle field. I will employ tactics closely resembling that of a modern day snipers modified to fit the smaller sized battlefields we have here on the west coast. As camouflage and concealment are of little value. Stealth, patients and accuracy combined with maneuverability and the element of surprise will have to do.

The Project - When combining the battlefield conditions and desired battle tactics, I have derived a set of specifications for a paintball marker. These specifications are not currently met by any of the existing commercially produced markers, hence the purpose of this project.

Specifications:

Stealth - The marker must be as quiet as possible without violating any local, state or federal laws and without depredating the range or accuracy. The marker doesn't have to be absolutely silent as we will be taking fewer shots, simply being quieter than machine gun Joe standing 20 feet away should suffice.

Accuracy - Less than or equal to 24 Minutes Of Angle (MOA) = approximately 8 inch group at 25 yards. I know this sounds like horrible accuracy, however in paintball terms this would be a supremely accurate marker. The maximum effective range for a paintball traveling at a muzzle velocity of 285feet / second is around 25 yards, beyond this the paintball is not likely to break on a soft target. An 8 inch grouping at this estimated maximum effective range should be sufficient to hit the center of mass on a man sized target.

Maximum Effective range - 25 Yards

Portability - The marker shall be light, small and compact as possible without degradation of the other requirements. Our battle tactics require the ability to move quickly in the event we are discovered. A marker with a large air tank and large hopper is unwieldy and difficult to maneuver.

Sights - Less than 10x magnification scope, specifically designed for air rifles. The eye relief should be sufficient for proper viewing through a paintball protective mask-greater than or equal to 3 inches.

Ammo Capacity - 10 rounds or less. If we are able to achieve the 24MOA accuracy, large capacity hoppers and tanks should not be necessary.

Reloading - The marker should allow for extremely rapid reloading of both paintballs and air supply.

The Road to Accuracy - After closely examining all of the theories, stated experiences and facts about what makes a paintball gun accurate or inaccurate I have come up with the following scoring scheme in order to better understand what makes a difference and by how much. The idea is that a score 10 would be as accurate as possible and a score of 0 would closely resemble a rental gun at your favorite field. At this point the following table is speculation, in the future I would like to apply minute of angle (moa) values to the various marker features for a more accurate representation of how accuracy is affected.

5 - Barrel and paint size matching
2 - Barrel Length
1 - Bolt Venturi Configuration
0.5 - Barrel Venting
0.5 - Barrel Rifling
0.5 - Compressed air instead of Co2
0.5 - Closed Bolt Operation

Barrel and paint sizing - This effects accuracy the most, proper paint to bore match will greatly decrease muzzle velocity variance and increase the paint ball stabilization during the acceleration process. Just like high precession shooting, we want to select the best ammunition possible. Fortunately with this system we do not intend to fire a zillion rounds during the course of a day, so we can afford to purchase the good stuff. After a lot of digging through reviews and specifications, I have selected the RPS Marballizer. Supposedly, the shell is slightly thicker and of higher quality than your average paintball.

I purchased a case of Marballizers and began sizing the individual paintballs, averaging around .686in. in diameter and slightly larger around the seam. I was able to use a barrel to paint sizing chart to narrow down my barrel selection.

Barrel Length - It was impossible to find any real facts that related to what the optimum barrel length should be, however, most of the opinions I found stated that 7 inches of un-ported barrel length with an additional 7 inches of ported barrel for a total length of 14 inches. Most of the opinionated answers I found stated that the first 7 inches would allow the paintball to stabilize, then the following 7 inches of ported barrel would reduce the amount of turbulence cause by blow-by. Sounds logical, so we will run with it, a longer barrel might allow the paintball to stabilize more, however, we need to keep the overall length down to meet our maneuverability spec.

Bolt Venturi Configuration - The shape and size of the bolt aperture has a small impact on how the paintball is accelerated and the presence of air turbulence.

Barrel Venting - Barrel Venting makes a small or minute difference in accuracy if your paint is properly sized to your barrel, i.e. you have less blow-by therefore the turbulence is less. Venting does more for sound suppression than accuracy.

Barrel Rifling - Rifling a barrel for a paintball has very minimal effects; a round ball has such horrible aerodynamics that spinning the ball has little effect on accuracy. If the rifling is done improperly or in the same manner as a normal firearm your accuracy will decrease due to more blow-by.

Compressed air instead of Co2 - The problem with Co2 is the transition from a liquid state to a gaseous state; this state change can cause pressure spikes and thereby affecting the repeatability of your muzzle velocity. In warmer climates this is less of a problem. Most of the modern markers have some type of expansion chamber that helps this transition reducing velocity spikes. Overall, changing to compressed air makes a minute improvement in accuracy.

Closed Bolt Operation - Closed Bolt operation affects accuracy in two ways; first off if you are able to avoid cycling of the bolt until after the paintball has left the barrel you will have less recoil and are able to stay on target. In addition, keeping the bolt closed during paintball acceleration will result in a more stable muzzle velocity. Overall, closed bolt VS open bolt has a very small impact on accuracy.

The Marker - The WGP Autococker is supposedly the most accurate paintball on the market, based on the above feature matrix the WGP Autococker with the right barrel and matched paint would score a perfect 10. So I went to the local paintball store and played around with the WGP Autococker, although a highly refined and well made product I found several things that I didn't like:

It appeared to be complicated to maintain and tune.
The addition of a 14 inch barrel and compressed air tank made it cumbersome and awkward.
I didn't see an easy way to mount a scope.

It quickly became obvious that the WGP Autococker was not what I was looking for. After a lot more searching I found a one of a kind product. A clip fed paintball pistol with a removable barrel manufactured by Tiberius Arms. The TAC-8 Pistol has a magazine capacity of 8 rounds; each magazine holds a 12g Co2 cartridge as well. The magazine design allows you to remove and replace the magazine without loosing very much Co2. The advertised spec is 3 magazine loads per Co2 cartridge (24 rounds). Actual testing revealed 22 shots per Co2@285 feet/second muzzle velocity (rapid fire). Initial chronograph test revealed a muzzle velocity of + or - 10 feet per second divergence from shot to shot. This initial test should be discounted do to the mismatch between paint and barrel. Once the new barrel is fabricated we will run another test to determine the average shot per shot velocity variation.

In theory, with the addition of a new barrel and some matched paint we can score the TAC-8 pistol with an accuracy rating of 9.5. This might be accurate enough to meet our accuracy spec. The TAC-8 is small, light weight and the addition of a 14 inch barrel will add about 8 inches to the overall length as 6 inches of the barrel will remain internal to the marker. Mounting a scope is easy and straight forward with the absence of a top feed hopper.

Paintball Ballistic Data

Paintball weight: 3.2grams / 49.38 grains
Paintball Diameter: 0.684in
Paintball Ballistic Coefficient: 0.0075

Stock TAC-8 picture from the Tiberius Arms Web Site

Before we can precisely measure the accuracy of the marker we require a new type of target specifically designed to work with paintballs. The underlining problem is when the paintball strikes a target it SPATS!!!. It's very difficult to determine the center of impact. We fabricated a 4foot x 4foot target box on stilts that uses plastic wrapping as the primary impact zone. The paintball should pass through the plastic and plat on the back wall of the box leaving a hole that we can accurately measure.

Initial mortifications complete, a new barrel fabricated and installed, we are ready to try it out.

The first accuracy test was absolutely amazing; the new barrel was absolutely silent. So quiet that I had to go back to the chronograph to make sure I was achieving the recommended 270 feet/second muzzle velocity. The chronograph revealed a muzzle velocity of 273 feet / second with a standard velocity deviation of +- 1 foot / second (even more amazing!!!) Firing a 6 round group at 50 feet with the stock plastic sights and the new barrel achieved an amazing 6.5 inch grouping.