mproving PTEnforcer Velocity

 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.

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.

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!