Improving PTEnforcer Velocity
by
Neild Bingham

  The PTEnforcer is one of a new trend in semi automatic paintball side arms.  It is basically an over/under blowback on the same principle as the Spyder type paintball guns except that it loads with a spring loaded feed tube and runs on 12 gram Co2 cartridges.

   I recently acquired a PTenforcer as a backup side arm.   I had read that the out-of box performance of this marker left a lot to be desired and they weren’t lying.  But being a tinkerer and being a fan on the simplicity of blowback markers I thought I’d give it a try.  Besides, it’s a sharp looking gun.

   The best velocity I was able to get out of my new gun was 190fps on a new 12gram.  Average velocity was running about 160 to 170fps cranked wide open (pretty dismal).  I immediately went to work on improving this.

Start with the obvious
  First I replaced the valve spring with a much lighter one I had in my parts box.  I went back to the chronograph only to find that it had no discernable effect.  Next I acquired a hammer spring from a Tippmann model 68.  This spring was heavier and longer then that in the PT.  I cut it down to just slightly longer then the PT’s but at the same time I made another change.  I wish now that I had done a chrono test on the hammer spring alone before made the second modification but such is life.

   This third modification is going to take some explaining so please bear with me.  One of the things I noticed when I took the gun apart was that the valve pin fit very loosely through the back of the valve.  The pin is shaved flat on one side the allow Co2 to pass into the hammer chamber for re-cocking much like that of a Spyder.   However there is also a tremendous amount of play around the valve pin as well.  I felt this was a bit extreme and that it might also be contributing to velocity problem (I’ll explain my theory later on).  To rectify this, and please don’t laugh yet, I took a spent 22 rifle cartridge and drilled a hole the same size as the inside of the cartridge through the back (I think I used a 13/64ths drill bit).  I inserted the drilled cartridge into the valve pin hole from the outside.  Then placing the valve, pinhole end down, on a flat surface I used a phillips head screwdriver and from inside of the valve I taped the open end of the cartridge flowering the end outward to hold it in place.  The fit was uncanny.  The cartridge fit both the pin and the pin hole creating a reasonably good fitting bushing.

The test
  I took the reassembled gun now with an extra light valve spring, a heavier hammer spring and the new bushing around the valve pin to be fired across the chronograph.  With a fresh 12 gram Co2 cartridge the first shot across the chrono registered 290fps.  WOW!  This was well beyond what I could have hoped for.  Even the early shots that followed ran in 270s and 280s.  I then decided to try and see which of the modifications had the most effect.  I removed the valve spring and hammer spring, replaced them with the originals, and took the gun back to the chrono.  With just the valve pin bushing in place the chrono readings ran in the 220 to 230 ranges.  I then placed the light valve spring back in the gun.  This did not appear to have any discernible effect.  I then put the heavier hammer spring back in and the velocities returned to the 270 to 280 ranges.  I did find, when running efficiency test, that though the lighter valve spring had no effect on velocity it did increase efficiency by two shots per 12 gram.  I have only guesses and theories as to why.

Speculations and theories
   I’ve been told that others have tried replacing the hammer spring with little or no effect on the velocity.  If my theory is correct then this is quite likely.  It was on the evening that I’d received and first tried out the marker.  It was a somewhat cool and damp evening so you could easily see the Co2 clouds as the gun was fired.  It was then that I noticed that a lot of Co2 was escaping from the ball feed area.  This is what clued me into what I believe to be the guns primary problem.  If I am right, then the bolt of the gun was opening long before the paintball left the gun allowing to much of the Co2 to escape.  This would explain why just replacing the hammer spring would have little effect and to were the bushing comes into play.  It is my belief that so much gas was passing by the valve pin that the hammer and bolt were opening to soon, depressurizing the barrel.  The bushing in effect slowed down the cocking process by reducing the amount of gas passing into the hammer chamber allowing the ball to leave the barrel before the gun re- cocked.  Now adding a heavier hammer spring could have the intended effect.

The Wrap up
  The modifications I made to this gun not only dramatically improved the velocity but the efficiency as well.  From 19 or 20 shots when I first got it to 23 to 27 shots (depending on conditions) before the gun fails to re-cock.  In short reducing the Co2 passage into the hammer chamber created no re cocking problems but instead improved it over all.  Next I hope to address the oversized barrel/bore issue by inserting a sleeve.  Not only should this improve accuracy but may add additional velocity and efficiency by allowing less gas to escape around the ball.  I’ll let you know how it turns out.

   The following is a velocity test chart.  In this chart the first shot was dry fired to alleviate the inevitable hotshot that comes when a 12gram is first pierced.  The gun was then fired, reloaded and fired until it failed to re cock.

On an unrelated note
  I have read that a number of players have had problems with the PT jamming forward when fired.  My gun developed this same problem and this is what I found.  The link pin between the bolt and hammer is short and is held in place by a spring and setscrew.  This places a lot of play in the pin and allows it rock forward and back during the cocking cycle.  This in turn creases the aluminum on the bolt in front and in back of the hole where the pin comes through.  This is how my gun was getting jammed.  The warped metal was wedging the bolt at the entrance of the breech.

To help reduce the rocking of the link pin I placed a small screw inside the spring between the pin and the setscrew and tightened the setscrew down firmly.  You’ll have experiment to find one just long enough to put pressure on the pin but not so long as to let the setscrew stick out passed the top of the bolt.  Only time will tell how well this will hold up.  A more permanent solution would be to install a longer pin that doesn’t rely on spring pressure to keep it in place.  I also removed the rear-cocking knob.  I’ve long thought it a bad idea to cock a paintball gun by pulling on the back of the bolt.  This method puts a lot of pressure on the link pin since the firing spring is behind the hammer and you are pulling on the back of the bolt.  In this case I’m sure it contributed to the damage to the bolt.

I hope the information in this article is useful. Play safe, have fun!