MarauderAirRifle.com

[Do99ie]

The only way I've found to increase the velocity is to increase the airflow through the entire gun. That may be a no-brainer but being somewhat new to airguns I probably have to learn all the things
old-timers already know. So I'll tell the story again:

I drilled the valve port out to .187 inches, made a copper transfer port (recently completed) similar in design to the original but massively larger with an inside diameter of approximately 0.2 inches
and about 5/16 inches outside. It required ordering some special square cut O-rings from The O-ring Store.com and tailoring them to 11/32 inches outside. I also had to mill both the valve and barrel
tops/bottoms to 11/32 inches with the end mill and drilled the barrel port to 0.187 inches as well. So basically the entire route from poppet to pellet is 3/16 inches in diameter. I tried to go to 1/4 inch
but that was too big and actually cut into the wrong area and ruined a perfectly good valve. Oops, but oh well, only one way to learn. So I learned a lesson. If I was a machinist and had the equipment
I'd invent a valve that could handle it but the best I can do right now is alter what Crosman Corp. sells. Saw one on JS Air rifles that had a 1/4 inch port but they evidently no longer sell it.