Have been asked about this many times will put it on my site soon but for now.
How to mod tube bulk for power.
The Tube bulk cap Brian and Associates as well as others sell this as part of a two piece tube bulk powerlet eliminator.
Drill 1/4 inch hole all the way trough the cap.
drill 25/64ths hole about 1/4 inch into the rear portion of the cap.
Cut two or three treads from the cap.
Drill out extra material from the front of the cap for more charge volume.
Cap from the rear
Cap from the front
Now combine this modded cap with the mods already available for the valve body ie; porting, stem mods and a lighter spring for some decent power upgrades. If you choose to use the stock Crosman tubes at high pressures such as 1200 to 1500psi be sure to pressure test them with the valve and cap installed. The valve and cap should be secured for safety. Just because some of us have used these mods at the mentioned pressure does NOT mean all of the tubes are safe at these prssures.
Don't blow yerself up be safe know what you are doing or just plain don't do it.
I used to have a life. But now I have the forum. I am a sick man?