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SMP · Silver Status Member

I just finished the final adjustments on a new FTP and valve and it's retaining air after 8 pumps. Enough air to take an accurate second shot.

I'm kicking myself for not having my chrony with me so I don't have any velocity numbers.

What's the solution here? Stronger spring?

Gippeto · Member

Do you want two shots...or one?

Lighter spring in the valve helps to dump more pumps, but you'll likely need to cock the gun prior to pumping.

Heavier striker spring will of course work as well...may I suggest a velocity adjuster? Bling is GOOD! Cool

Al

SMP · Silver Status Member

I've seen and read about velocity adjusters. Can they be purchased or do the have to be made by drilling and threading the end cap.

Ideally I would like it to dump it's air in one shot so that when I pump the gun X times I end up with a known velocity rather than (X + retained air)

Unless if the velocity becomes stable regardless of the retained air then I would be happy with that too.

rsterne · Moderator

Never heard of a 1377 retaining air in 8 shots unless there is a hammer problem.... With stock springs you should be good for about 14 pumps or so without retained air.... With a lighter valve spring and/or a heavier hammer spring more than that....

Have a look to see if the hammer is hanging up somehow.... bad sear, sear dragging on the hammer, burr on the tube, kink in the hammer spring, something....

Bob

Gippeto · Member

Springs are cheap (like me Laughing

), and I would suggest trying that first. See how it works for you.

Velocity adjusters are available, not sure who's making them for sale. I'm sure someone will pipe up with a maker, or an offer.

Al

Edit: Bob replied while I was typing...good thinking Bob...if you installed a steel breech and did not shorten the rear breech screw, this may be binding up the striker spring.

SMP · Silver Status Member

Thanks fella's

I will open it up and give it a thorough look tonight.

The rear breach screw is barely engaged as I used the factory rear sites and had to do some substantial filing on the sight to get the screw to engage threads at all

SMP · Silver Status Member

Well I disassembled and had a good look tonight. The spring was okay. the screws were not protruding and the hammer showed no signs of hanging up on a burr or the sear.

So I lightly polished the piston in a cross hatch and buffed a very light lubricant (synthetic machine oil) onto it and put it back together.

That must have done the trick because it's not retaining air at 14 pumps. I didn't go any further because I will never have need for that velocity.