A Quest for Paintball Accuracy

Robert Judson

In the Beginning:
Several years ago as I went to play paintball with my boys that were teenagers at the time, and we all got hooked on paintball. I had no idea how much fun it would be, and little did I know where this one game of woods ball would eventually lead. Having stepped over from my comfortable corporate chair to the “Paintball World”, my boys were elated and mom became a “Paintball Widow”.

After the first couple of weeks of playing, I vividly recall playing recreation ball in the woods, and having a shot at a player with my trusty rental marker only to have the paintballs curving so much, I simply could not hit targets 30 meters away. I own a hand-made Johnson 22 target rifled that can hit within ¼” at 100 yards, and here I was trying to shoot my opponent 30 meters away and the balls would drift away from the target. A young teenager had embarrassingly zippered me with balls as he bunkered me. That was the day my engineering mind said to me “What will it take to make my gun shoot accurately?” My knees are damaged from running Marathon’s so I had better be able to hit what is running at me. I asked my son, why didn’t my marker shoot straight? Why couldn’t I hit what I pointed my marker at? The 19 year old referee from the Tourney Circuit commented we needed to get those expensive electronic markers with Nitrogen, and add a high speed hopper, with an expensive polished barrel to achieve accuracy. I thought to myself, there’s got to be more to accuracy than money. I went out immediately and purchased all the expensive gear, barrels, hoppers, and you name it, only to find, the accuracy I was looking for was not achieved. The concept of improved Technology did get my attention. That was the beginning of spending my Saturdays and evenings in the warehouse and shop tinkering with barrels, markers, various types of air tanks, high speed cameras, etc. Accuracy had become my hobby, my passion, and is what started our “Quest for Accuracy”. The Hammerhead barrel began with a simple quest to make a barrel that would allow an old man the ability to compete with his kids. Four years latter, Hammerhead is on its 4th generation of rifled barrels. We started this endeavor for the sole reason to improve paintball accuracy, so an old guy with damaged knees could compete with his kids in the game of paintball. The one barrel has grown to thousands and has turned into a humble family owned business. This is our story of “Hammerhead”, producer of the rifled, counter-bored and reverse ported barrels.

Speedball/Woods and the Multitude of Markers:
With time, my boys and I continued to play paintball. Some grew to prefer tournament style play while one of my boys became more focused on “Woods and Scenario” games. Marker types in our house eventually grew to include Tippman’s with Flatlines, Spyders, Angels, Phantoms, Ion’s, Impulse’s, Ego’s, Mags, and Timmy’s. I encouraged the boys to try out every type of marker we could get our hands on. Each boy believed “Their Marker “shot the best. Without a method to test, making bold statements such as I shot 5 guys out today, and that’s 2 more than you, was not the scientific approach to determining accuracy. So, buying different markers and barrels did not resolve the issue of accuracy. However, our arsenal grew with no definitive answer to accuracy.

Frustration and Exacerbation:
Many Euros latter it was now quite clear and succinct that “More Expensive” did not prove “More Accurate”. Many markers and barrels latter having tried high-pressure, low pressure, short barrels, long barrels, cheap paint, expensive paint, we were no closer to our quest for accuracy. We paralleled our studies with on-line chats and literary searches only to find as many opinions as questions. We were told long barrels are more accurate, others told us shorter barrels, some told us the sizers were the answer. We were continuing beginning arrive at the conclusion, “To understand the dynamics of paintball accuracy”; could take some serious research and data collection.

Data Collection and Information Search:
We began to question players and storeowners as to why some paintballs would fly straighter than others, would different markers and barrels actually shoot better, and asked what analytical tests were available to show comparisons between the various types of equipment and paint. We were unable to find much recorded data to back-up claims. We found reports showing barrel comparisons, pattern types, and reports of hitting a pie-pan so many times at a distance, but could find little comprehensive studies, that used a “Standard Method” for testing markers and barrels. Industry standards in the field of Engineering and Construction are typically established for standardizing tests and termed “Standard methods” for testing concrete, steel, chemicals, Ph, Acidity, Wastewater,etc. We did not find a standard method of testing of paintball equipment.

Is anybody out there?:
Some excellent research has been done for the paintball industry. Tom Kaye of “Airgun Designs” and several other paintball industry leaders have done excellent work toward paintball research. However, to our knowledge, we could not locate a central research facility dedicated to the sport of paintball with a “Standard Methods” for testing. Independent companies have developed much of the work done to date and that is most likely maintained confidentially to protect private interests. This is probably due to the expense and time required to collect the data, and manufactures that collect and expend significant funds to acquire the information, choose to retain the information for their own private use. Why give the recipe away for Pepsi, Coca-Cola, KFC Chicken, etc?

We simply wanted to know, what were the variables effecting paintball trajectories without bias. Was it the marker; was it the barrel, the paint, the type of air, just what was the answer? We also wanted to know what standard method of testing paintball accuracy existed. If there was not a standard method for accuracy testing, we would then need to develop a method to gage process improvement differences, standard deviation, develop upper and lower control limits, which would provide statistically accurate and repeatable methods of testing. With no standard methods for testing, we decided we would develop our own testing methods and collect our own data. We were determined “We will see it when we believe it “the data that is.

Targets and Data Collection:
We needed a reliable and repeatable method to test markers, barrels, and ball seizers. The system needed to be simple, repeatable, and accurate. We wanted to define and isolate the dependent and independent variables effecting paintball trajectory. We knew we needed to minimize the variables including marker pressure, ball size and shape, porting, barrel lengths, velocities, etc. Also, what were the effects of maker type on the results? We chose to analyze the data using statistical methods and compare the results using an agreed to formulas. We assumed the simplest evaluation criteria would be mean diameter hits from a centroid with a standard deviation calculation. We also knew we needed to run tests quickly with immediate results, and make changes quickly to the system to optimize our study efficiency. We chose to use excel spreadsheets for data collection and use the standard equations for determining standard deviation.

Initially, we shot paintballs into styrene insulation panels. The paint would penetrate the panels, and we could then measure the distance from the centroid of the target for accuracy using a clear Plexiglas sheet with concentric circles with increasing radius of 6” increments. However, this process proved to be very time consuming and expensive. We modified our testing procedure to include a digitized electronics board similar to those used in the drafting business. We modified an old electronic board and wrote our own software for our “Electronic Digitizer Target”. We overlaid the board with a thin metal sheet, and covered the sheet with the Plexiglas. Ball impact would be indicated on the computer screen when acted upon by a ball. The data would download showing all strikes on a PLC. Each time the ball would hit the target it, it would record where the ball hit, and it would be entered into the spreadsheet. We could run a test, wipe the board off and run another test quickly.

Markers were bench-mounted in a vice, and a short wooden fulcrum activated the trigger. Each test consisted at least 40 shots in order for the test to be statistically accurate. The excel program was then used to calculate standard deviation, average diameter and was used to graph probability curves. This equipment provided us with immediate and accurate feedback.

Ball Velocity:
Velocity was measured using a bench mounted chrono with a digital readout. We set the screen at 3” to 4” from the muzzle we also had a hand chrono to verify chrono accuracy. The chrono was calibrated before we started our testing. We compared the two chronos' and found that they were within 3 to 5% of each other. All tests were calibrated to approximately 280 ft/sec. All testing was done at 120 feet. We utilized tripod mounted radar for measuring ball velocity at the target. We found that a change if 5 ft/sec in velocity at the muzzle could vary the accuracy at the target by 2.5 to 3 inches. We found some of the misshapen paintballs provided a variance of 10 to 15 ft/sec and affected the accuracy by as much as 6” to 9” from the target center. We also attempted to size the paint with the barrels. We found that the velocity of the balls left the muzzle at 280 ft/sec, but slowed down considerably to approximately 100 ft/sec at target impact. Time of travel to hit the target was measured to be less than a second... The balls slowed due to drag on the ball due to air resistance. (We will discuss drag forces latter). Trajectory variables from variables effecting velocity were:

Trajectory Factors:
  • Variable Effects on Velocity Deviation from Target ( ft/sec) (Inches)
  • Oblong-Misshaped Balls 5 to 15 ft/sec 3" to 10"
  • Paint-Sizer Mismatch 5 to 20 ft/sec 3" to 12"
  • Inadequate Porting 8 to 12 ft/sec 4" to 6"
  • Regulator Fluctuations 10-15 ft/sec 5" to 7"
  • CO2 Tank drop of 15 Degrees F 40 ft/sec 20" to 24"
  • 30 Degree Temp Barrel Drop-C02 60 to 70ft/sec 25" to 38"

Ball Quality:

What was the effect of ball quality on accuracy? Is a paintball a paintball is paintball, or does the ball effect accuracy and if so, how much? Ball quality was a serious concern. The variation of paint quality, ball size variation, ball shape, seam sizes, etc could affect ball velocities and trajectories significantly. The question is how much? We evaluated several paint types, and found out quickly, that the ball diameters and shapes of competing products varied differently, and the ball sizes of paint contained inside one bag was found to vary widely depending upon the supplier and batch. We also found paintballs that were not completely filled and had voids in them. We did not want to measure ball accuracy with balls varying in mass and centers of gravity. We measured diameters, weights, and rolled the balls to check for empty pockets. We then chilled the paintball to 34 percent and dissected them to determine how much void was present in the balls that rolled unevenly or the mass was less considerably less than the sample. It made sense that balls with voids could pose problems with a center of gravity that is off-center, and could lead to ball trajectory variances.

We also noted that different paints had various types of seams, dimples, football shapes, and various imperfections. We did not want the ball quality and ball size to effect our conclusions from our testing. We also noted that many paintballs were oblong and misshapen. We also noted that the seams and dimples, and various edges on the paintballs could affect the aerodynamics and drag on the balls, causing them to spin, or move erratically. We know that the aerodynamics resulting from an oblong ball, that pressure differentials on the back of the ball could cause the ball to move in erratic and in non-liner paths.

After sizing our paint we ran tests to measure the velocity differences due to variances in paint size and weight. We found slight variations in ball size, mass, and shape could vary the ball velocity by as much as 15 ft/sec with a corresponding effect on accuracy of approximately 8” to 10” from the target centroid. While we could spend weeks analyzing paint types, we chose to conduct all of our tests using Green/Black Marballizer. (49.0) gr. To minimize the variation in our testing due to ball size. we made stainless ball sizers using a laser. The stainless sizers worked similar to those used in sieve analysis in sizing sand and gravel. The stainless plates were 1/8 inch thick. We made a series of plate sets. Each set of plates had a series of holes cut of similar size. We made a series of plates ranging from .679 to 0.693 inches. We then sized the paint by placing the paint through the larger screens, which passed subsequently through the smaller screens, until the paint would not fall to the next screen. We then pulled off the balls that measured between 0.688 and 0.690 for our testing. The purpose was to limit ball diameter variation and remove one very critical variable from our testing.

Our final testing was done at using controlled temperature and humidity environment thus minimizing the effects of swelled and soft paint. We initially ran tests outside in the Texas heat (100 degrees F with 90% RH) and observed series ball swelling. The accuracy tests run in cold weather did not compare well to the summer tests and were not repeatable in the laboratory. This could lead us to the conclusion that temperature and humidity affected our tests and resulted in all final testing being done at 72 Degree F with 65% RH. At colder temperatures, the balls may become harder, and react with the barrel differently than balls at higher temperature, and the density of air is greater with cold air, affecting the ball drag.

Air Supply:
We found the CO2 had the tendency to absorb the heat from the barrel when rapid shooting occurred and the velocity would decline. The corresponding drop in barrel temperature of 25 to 30 degrees F was affecting the velocity by as much as 40 to 60 ft/sec. A quick look at the basic gas laws including PV=nRT and the subsequent following equation of P1/T1=P2/T2, it can be calculated that a 5 to 10 degree change in temperature and pressure can result in velocity change of 10 to 15 ft/sec. However, we saw much larger swings in velocity than the Ideal gas laws predicted. Evaluating C02 enthalpy chart with the ideal gas calculation could in fact show much greater velocity differences. Because CO2 is not an ideal gas, we believe the Ideal Gas comparison does not apply. At 120 ft distance, the 40 to 60 ft/sec velocity difference was producing a miss of as much 36” to 48” and more... Because of this, we selected compressed air for our testing and used a large 150 lb air tank for our air supply source.

For video, we initially used a digital Sony high-speed camera with a strobe and found we needed much higher speeds to capture ball rotation and ball deformation in the barrels. The high speed camera we used is a Phantom V7 and was capable of taking digital pictures at the rate of 10,000 frames a second. The camera allowed us to evaluate the effects of ball rotation. We used the camera to capture the effects of air transfer at the muzzle as the ball approached and passed thru the porting to the muzzle exit. We also used the video to observe the ball rotation for varying rifling rates, and study the effects of varying ball sizers.

Conditional factors effecting Paintball flight?:
We ran most of our tests inside an air-conditioned building, where we could hold a temperature of approximately 78 degrees with approximately 60% RH. Since the density of air changes with changes in temperature and Dew point, it was important to attempt to test under the same atmospheric conditions for every test. Air density is affected by altitude and is a component of the air drag equation. Since all our tests were at the same location, this was not a factor for our testing. Our mounting bench was approximately 4.5’ tall. The paint and barrels were all equally sized. (All bores were 0.690). We measured the bores using stainless bore plugs accurate to within 1/10,000 of an inch, and using high-end digital calipers and our ball sizers. We used fresh marbalizer paint for all our studies.

Learnings and Results?:
  1. What affected the Trajectory and Accuracy the most?
    We found that there were accuracy differences in marker types. We found accuracy to be effected by factors including the markers, barrel types, paint quality, barrel to ball matches, etc. The entry level markers could not shoot nearly as fast as some of the expensive high end electronic markers, however, all the markers shot well as long as the barrels, ball sizers, and the paint was good. As a result of the testing, 1 of my sons shoot an Ego, another shoots an Angel G7, a thirds shoots a Tippman A-5, and the 4th shoots an Ion.
  2. Barrel Length Effects?
    Once you pull the trigger on the marker, pressure is exerted onto the ball. This pressure acts upon the backside of the ball in the form of a pressure wave and accelerates the ball. This pressure wave has a definite shape for each type of marker, and can effect how the ball is accelerated in 5 to 6 thousands of a second. If you study Boyle’s law of partial pressures, you can calculate how far inside a barrel gas will expand before the pressures on both side of the ball are theoretically equal. Where the pressures on both sides of the ball are equal marks the effective useful length of the barrel for energy transfer. Depending upon the barrel diameter and marker type, the effective length of a barrel is somewhere between 6” to 8”. Porting on the breech side of the barrel that is less than the effective barrel length reduces air efficiency. Barrels longer than the effective length provides other benefits to players including aiming, porting, rifling, pushing the bunker out of the way, etc.

    We found the shorter barrels (6.5”) provided more consistent velocities than longer barrels (14” and 16”). However, for the 120’ tests, we found the longer barrels to be more accurate than the shorter barrels even though the shorter barrels provided a slightly improved velocity average than the longer barrels. We found that a change in velocity at 120 ft of 5 ft/sec would change the distance from the target centroid by approximately 2.5” to 3” with the longer barrels. However with the shorter barrels, we found them to very accurate at shorter distances with a more uniform velocity than the longer barrels. However, the shorter barrels did not produce the more accurate results at the longer distances even though the velocities with the shorter barrels were more consistent.

    We found the shorter barrels were approximately 8% more air efficient than the 14” barrels. Greater turbulence may exist at the barrel exit with the shorter barrels and/or the longer barrels (14” vs 8.5”) may simply provide greater ball orientation and ball rotation before the ball exits.
  3. Effect of ball sizer on barrel accuracy?
    The purpose of ball sizers can be simplified by simply stating “The purpose of the ball sizer is to transfer".
    We conducted statistical tests using our electronic digitizer in conjunction with our high speed camera to determine the effects of sizer length on accuracy. In simple terms, is there a relationship with sizer length to accuracy and if so, what is that relationship? In order to determine these relationships, we made ball sizers that varied in length from ½ inch up to 8” in increments of ½”. We then took 40 balls which were sized using the our ball gauges, shot 40 presized balls at the electronic target at 40 meters for each set of sizer lengths. During each test, each ball strike was downloaded to the PLC and loaded into a software program to determine average hit diameter, standard deviation, and upper and lower control limits. We used Marbalizer with an average ball diameter of 0.690 for our tests, with a target velocity of 280 ft/sec. We found ball sizers with a length less than 2 to 3 ball diameters provided the tightest ball grouping and the smallest standard deviation. The longer the sizer we found a decline in the standard deviation and ball groupings. (Less accurate). The longer ball sizers produced a larger variance in ball velocity than did the shorter sizers . The short ball sizer (½”) was significantly more accurate than a sizer 4” to 8” in length. How was the length of the ball sizer affecting the ball accuracy and ball velocity? Was the longer sizer creating more drag on the ball? Was the longer sizer deforming the ball? What was going on?

    In order to answer this question, we needed to observe the balls and measure the ball velocities at the muzzle exit for each sizer length. We took our high speed camera (10,000 frames/second) and shot paint from the same maker using varying sizer lengths with no barrels. We wanted to know what effect the sizer had on the ball, not the sizer and the barrel. We found that the short sizers had more consistent velocities than the longer sizers and produced significantly fewer “Zingers” (Balls going out of control). The high speed photos show the shorter sizers develop less ball rotation on oversized or large seam balls. The shorter sizers without a barrel have more consistent velocities and less ball spinning. We believe this is due to the ball having less time and surface area to interact with the sizer. The short sizer allows the flexible ball to deform and then rebound more quickly than a long sizer. It is most critical to understand, “The Only Purpose of the Sizer” is to allow efficient transfer of energy from the tank to the ball. . Deforming the ball in a long sizer can cause the balls to grab the sides of the barrel and spin out of control, or change the ball velocity. Spinning paintballs out of control or changes in velocity (or both) will definitely vary the accuracy of the ball in flight. The high speed camera recorded t extremely high rates of speed (10,000 RPM), and cause “Zingers”, more often with the longer. The short sizers provided more consistent velocities with less ball spin when paint was sized correctly.

    We believe the larger seams have the tendency to grab a longer length sizer and spin out of control much more easily than a shorter sizer. During the sizing process, we believe friction results causing the gas losses. The shorter sizer had a more pronounced improvement in air efficiency with the seamed paint. The smoother paints with less dimples provided improved accuracy and less differences in velocities with both lengths of ball sizers. The shorter sizer shot more accurately than the longer sizer in general.

    We did not study the effects of paint that did not match the bore. We believe, that once the ball does not match the sizer, velocity differences between shot to shot can exist, and slop between the barrel and the ball can cause the ball to spin out of control and for air to escape around the ball causing changes in velocities. The study of balls that did not match the barrel is beyond the scope of study.
  4. What are the effects of porting on marker accuracy?
    We found that porting significantly affected the accuracy of the barrel. Properly ported barrels and counter-bored barrels performed better than conventional barrels consisting of perpendicular, small opening porting. Our studies show pressure differences in the barrel and the atmosphere exist and vary with the porting design and shape. We also noted that the angle of the porting, and the cross sectional area of the porting affected the accuracy and the pressure in front of the ball measured at the muzzle... The slow motion video in combination with pressure sensors along the length of the test barrels showed that the air would exit and re-enter reverse porting as the ball would pass by the porting. the ball pushes air out of the barrel as it moves down the length of the barrel build a pressure wave in front of the ball, and is drawing air in behind the counter-bored and reversed porting it as the balls passes the reverse porting. As air enters in the porting behind the ball, the pressure adjacent to the ball comes closer to atmospheric allowing the ball to regenerate to its original shape before the ball exits the barrel if the angle and the size of the porting are adequate.

    Our studies show reducing the pressure wave by with reverse porting and counter-boring improves barrel accuracy. The improved accuracy is due to less turbulence at the barrel exit. Pressure differential at the muzzle exit results in turbulence at the barrel atmosphere interface. We have determined the counter-boring of the barrel in combination with the reverse porting reduces the pressure and turbulence in front of the ball. We have also determined that the counter-boring results in a larger barrel diameter at the muzzle. The larger barrel diameter results in a reduced pressure section and allows the ball to regenerate (go back to the round shape) before the ball exits the barrel.
  5. C02 versus Nitrogen?
    After completing our theoretical gas evaluation of CO2 versus Compressed air, we decided to use compressed air due to the calculated velocity changes, which we anticipated due to calculated temperature, and pressure changes in the barrels due to the use of CO2. We noted that the Compressed air system shot more consistent velocities than CO2 especially when rapid firing. During rapid firing, the barrel temperature dropped by 10 to 30 degrees or better. We found the velocity reductions of 25 to 30% with barrel temperature drops from 80 degrees to 50 degrees and a velocity drop from 280 ft/sec to 223 ft/sec. At 120 ft with the 30 degree change in barrel temperature, the target centroid was missed by as much as 3.5 to 4 ft. The temperature differential was due to the temperature changes from the CO2 gas expansion. We found that a 5% or 6% drop in temperature of the C02 tank, the pressure would drop by almost the same percentage. This was most likely due to the endothermic process of carbon dioxide expanding and absorbing heat as it expands which cools the barrel. We found the difference in Compressed air and CO2 produced marked velocity and accuracy results.
  6. Forces effecting Trajectory
    Once the ball leaves the barrel, there are forces acting on the ball. There are many variables that can affect ball trajectory including ball quality, seams, ball density, centroid of gravity, ball size and shape, gas type, and air temperature. However, there are also external forces such as gravity, drag forces on the ball (effected by a drag coefficient and Reynolds number) and ball velocity.

    Other forces are present including the Magnus effect or the aerodynamic effects of spinning. As the balls passes through the air, the effects of gravity are pulling downward on the ball; the air that strikes the ball tends to slow the ball down as the ball is acted upon the projected area of the paintball path. As air strikes the ball, the air moves over the ball and turbulence and wake are generated behind the ball as a result. This wake can change location on the back of the ball, causes uneven forces on the ball, resulting in the ball to move sporadically like a baseball players “Knuckle-Ball”.
  7. How does rotating the ball affect the ball trajectory?
    One of the challenges with defining paintball trajectories, is not only the many factors and forces previously discussed, but the fact that a paintball is like an M&M on a hot sunny day, while it may not melt in your hand, the ball is made up of a hard shell on the outside with a viscous liquid inside. The liquid and the shell do not necessarily spin at the same rates. Differences of rotation rates between the shell and the liquid are affected by the viscosity of the liquid and temperature.

    While we are not going into depth into the rotation and spinning of paintballs in this study nor are we delving deeply into what happens inside a barrel from the breech to the muzzle. We will disclose the fact that we rotated balls at varying speeds from 1,000 RPM to approximately 10,000 RPM. We rifled barrels with varying degrees of twist and depth grooves to determine how varying rotation rates affected ball spin and ball trajectory.

    The theory behind our study was based on the assumption that we had a relatively smooth ball that we could rotate. With ball rotation, a gyroscopic effect could occur improving the paintball flight. The paintball flight path could improve due to the rotation effects on the drag behind the ball which could be evened out. Another theory is that with the rotation of the ball in one direction, even if that rotation is slight, the ball could have a less of a tendency to change its rotation or direction after being placed in motion. We believe the eddy currents tend to form a coned zone behind the ball and hold the eddy currents at home during the paintball flight. This reduces drag and improves ball accuracy.

    We found the rifling needed to be done with a precisely correct depth and width of grooves and lands. This was needed to achieve required ball rotation, and the ability for most paints to self clean themselves after paint breaks. (Some paints will not self clean, but many will by flowing broken paint down the valleys of the rifling). We also found the rate of rotation and the velocity was critical to rifling performance. We finalized the rate of ball rotation with the targeted ball velocity of 280 ft/sec. Once the ball rotation exceeded a specific RPM, the ball tended to wobble at the longer distances. At the higher rates of rotation, we believe the shell spins faster than the paint, and the paint then absorbs the energy of the spinning shell. The Hammerhead barrels rotates the paint in a clockwise rotation simultaneously with a “slight” backwards rotation. We are gently rotating the balls in both directions and do not claim nor do we want to spin them. It is a very gentle ball rotation to achieve the accuracy. Hammerheads rifling does in fact rotate the ball in two directions and we found we could significantly improve the ball accuracy and get 20 ft or farther distance with a slightly flatter trajectory than a standard non-rifled barrels. We can only speculate that by rotating the ball, the drag behind the ball was made more uniform, and reduced the overall drag on the ball. Reduced drag and counter-rotation with a slight back-spin combines to make the ball fly slightly father and straighter.

    The ball rotation tests showed improved accuracy with a “Specific Rate” of rotation in conjunction with proper porting and ball sizing. Above or below the “Specific Rate” of rotation, ball accuracy improvement was not observed consistently.
  1. Ball quality-Is paramount to accuracy. Buy good paint if you want to shoot straight. Even the best marker with the best barrel is going to have a tough time shooting dimpled, seamed, and swelled paint.
  2. Barrel Type-The barrel is critical to the marker accuracy and second only to ball quality. A critical aspect of accuracy in our opinion is the internal barrel finish, porting and rifling. Hardness of the barrel could affect the longevity of the internal finish, but was found to have little effect on accuracy. (Do not confuse barrel smoothness with Grinnell Hardness of the barrel material.)
  3. Porting-The porting of a barrel is very important. Holes in the barrel for porting must be sufficiently sized and angled to allow ball regeneration and atmospheric balance prior to the ball exiting the barrel. Porting of the barrel closer than 5 or 6” to the breech wastes air. We found counter-boring of the barrel with reverse porting provided optimal results.
  4. Sizer Length-The shorter the sizer, the more accurate for most conditions.
  5. High-End Entry Level Markers-Shoots well when you match the barrel and paint. (Electronic markers can typically shoot faster than the lower end mechanical markers.) Many of the high end markers provide regulators that provide a more consistent air supply and velocity than some of the less expense markers tested, thus accuracy was more uniform, but not always. Some of the Spyders and Ions shot as accurately as some of the high end markers.
  6. CO2 or Compressed Air? -Gas laws say the Compressed air to be a more reliable gas for accuracy than the CO2. Our tests showed this to be true.
  7. Rifling Effects-The rifled barrel performed extremely well with lower rotational speeds in conjunction with proper porting and ball sizing. We found we could get approximately 20 more feet of ball travel with the rifled barrel with reverse porting with counter boring. We found the Hammerhead to self clean in many paints,(not all), and because the ball rides on the rifling with less contact area with the barrel, approximately 15% less air is required to operate.
This report was for the player that is interested in learning some basic principles about the aerodynamics of paintball. Had we had more time and funding, we could have delved into the Magnus effect of spinning paintballs, discussed Reynolds Numbers, coefficients of drags, dimpled vs. smooth paintballs, Newton’s 1st and second Laws of Motion, boundary layers, laminar flow, etc however, that was not the purpose of this paper. We wanted some simple basic answers that would assist us in making decisions regarding Markers, tanks, and barrels.

We are not going to compare the marker or barrel results to avoid manufacture bashing. . We do not want to take away anything away from the many good manufactures of guns or barrels. We do hope the average player can read this report, and learn something from our efforts.

A major learning for us was the recognition of the lack of a standard testing method for comparing analytical tests for the Paintball industry. It would be beneficial to players for the industry to develop a standard testing method for markers, paint tanks, and barrels.

Markers Tested:
  • Ego
  • Ion
  • Cocker
  • Angel G7
  • Spyder
  • Tippmann 98, A-5
  • Bob Long Intimidator

About the Author: Robert Judson is a Registered Professional Engineer, with a BS and Masters in Engineering. In his early days as an Engineering Manager with PepsiCo, he conducted R&D testing and wrote technical papers. He has written articles for the AMI, Baking and Snack, Engineering News, etc. He is presently President and COO of Emergent Construction Technologies in Dallas Texas responsible for Food Plant Design and Construction. Robert and his wife Donna have 4 sons and a daughter. Paul Judson, Robert’s Son, is co-author of this paper. Paul personally conducted much of the research collected during the last 4 years for the barrel development. Much of the data collected during this study led to the development of the Hammerhead Rifled Pro-Series, and the rifled, gun-drilled, and counter-bored Battlestikxx Recon barrels.