valve mod question

[oconeedan]

I have read about cutting a thread or two from the threads on the valve...I am guessing this reduces volume, and therefore you get higher pressure with fewer pumps?  I have also read about adding a washer, I assume inside the valve, further reduces the volume?

Theoretically, I would guess that a large volume valve, lots of pumps, and long barrel, are going to get the max power, at any cost.
But I typically like to shoot with 5 to 10 pumps, 5 for plinking and 10 if I want some power.  What would I do to get max pressure (power) at around 10 -15 pumps?  Lower volume, I assume?

I have made my valve to a flat top, use a flat top piston, and have opened up the transfer port.  At 20 pumps, I am just beginning to retain a bit of pressure in the valve after the shot.  That's ok, I rarely pump that much, mainly to "see what happens".

Still tinkering around with it.

Thanks in advance.  Dan

[airriflenut]

Dan, here is a link to some 1377 check valve length testing I did.  Basically compared a short check to a long check, and any gain/loss in each.  I hope this is some helpful info for you.

http://www.crosman-air-pistol-owners-forum.com/board/index.php/topic,14340.msg188290.html#msg188290

[arkmaker †]

There is a thread somewhere in this forum about maximizing for 4-5 pumps. Author was Full Sail?? That doesn't sound quite right, but if I can find that thread I will post a link. As I remember it he was getting very good numbers with minimal pumping. Odds are you will end up hating that gun when you need to pump 20 times for full power 


It was DaySailer    Here is the link;
http://www.crosman-air-pistol-owners-forum.com/board/index.php/topic,9762.msg113975.html#msg113975

[ped]

cutting the threads increases volume so will need more pumps to get upto the same pressure as an uncut one
ped

[oconeedan]

Thanks for all of the replies, and your time.  Let me go through the links you sent...
Dan

[Jauvesst]

my 1377 is currently set up to shoot at a flat 400 fps at 4 pumps with 7,33 grain match wadcutters and 500 fps with 10,34 grain domed pellets at 10 pumps for the longer outdoor shots.

setting it up to 4 pump operation is something im real happy about, pumping 10+ times between each shot got old real fast

[airriflenut]

my 1377 is currently set up to shoot at a flat 400 fps at 4 pumps with 7,33 grain match wadcutters and 500 fps with 10,34 grain domed pellets at 10 pumps for the longer outdoor shots.

setting it up to 4 pump operation is something im real happy about, pumping 10+ times between each shot got old real fast

That is interesting.  I've not thought about setting mine up that way, it may already be there but I'll have to do more chrony tests.  It will have to wait for now, working on regulators currently.