Getting a 312 to "dump" more air?

[BrushPopper]

Got a '63 312

Still a solid shooter, will sling Hobbies @ 640+.
I know that it's common for these valves to retain pressure after firing. This one retains abt 2 pumps worth of pressure, after firing.

Pump it 10, thereafter it gets topped-off with 8, in between shots

Has anybody had any luck/improvement by lightening the outlet seal spring?

BP

[avator]

I've had luck with other 3XX guns by squeezing the conical spring in a vise to the point of coil bind. I hold them there for 10 seconds or so them put them back in the valve. If you go too far you might have to cock the gun before pumping or stretch the spring back out a bit. I haven't had much luck with replacing the hammers spring alone.

[TerryM]

  The valve mods I showed in my post a few threads down increased my velocity a bit.  Lets air out just a touch faster, you might give it a try.  I am going to do the same with my 342.

[TerryM]

  Just put new seals in my 342 and modded the valve, didn't see any improvement in velocity.

[avator]

Good job Terry... I'm not a huge fan of doing irreversible mods to these vintage wood and metal pumpers... save that stuff for the Dasiys...... oops, my bad.

[TerryM]

Got a '63 312

Still a solid shooter, will sling Hobbies @ 640+.
I know that it's common for these valves to retain pressure after firing. This one retains abt 2 pumps worth of pressure, after firing.

Pump it 10, thereafter it gets topped-off with 8, in between shots

Has anybody had any luck/improvement by lightening the outlet seal spring?

BP

Shooting Hobbies at 640, no room for improvement.  Residual pressure is good, it works for us.   Sounds like you have a primo shooter.

[floydlong]

I realize this is a month old thread but I picked up a sweet little Benji 317 last week and it wouldn't pump air. I cleaned the pump arm and tube and replaced the pump cup. It pumps fine now but it only dumps a portion of the air from the valve. I haven't chronied the first shot yet but it seems hard. Then there are two or three residual shots remaining in the valve. I put a healthy dose of 30 WND oil in and pumped and let it sit vertical all night. Seemed to help a bit. Will just keep trying and see if it works itself out. There is a puff of air in my face at each shot??

I just went out to chrony it. AMAZING!! All of the shots were on 6 pumps. No more pumping, just cocking, loading, and shoot.
6 pumps: CPHP -
Shot 1 - 418 FPS
Shot 2 - 470 FPS
Shot 3 - 406 FPS
Shot 4 - 348 FPS
Shot 5 - 208 FPS
Does this mean if I can get it to dump ALL the air in one shot it will be 1850 FPS???
Any suggestions??

[avator]

Gotta love them "tootsie Rolls".

[floydlong]

I agree, Bill. Wish I had a dollar for all the ones I've acquired and sold. I may keep this one. If I lay it in my lap upside down I can get 6 pumps in her without much effort. More than that strains the old incision. She is sweet.

[TerryM]

  I have seven pumpers over 50 years old.  Some retain air, some don't.  A Crosman 110 is one of the two hardest shooters.  The 140 will shoot faster but the trigger becomes difficult at higher pumps.  The 110 shoots right around 600 fps with six pumps and is more accurate.  It retains air with more than five pumps but outshoots my other old Crosmans and Benjamins in spite of it.

[avator]

Terry, I have several vintage pumpers but your list impresses me every time I see it. Nice collection !!

[TerryM]

Terry, I have several vintage pumpers but your list impresses me every time I see it. Nice collection !!

  I've put my collection together just in the last six or seven years.  Always enjoyed guns and shooting but couldn't afford to collect firearms.  These, I've found, are affordable and fun.  I shoot all the time in my back yard.

  My Sheridan turns 50 in August.  It outshoots all the rest, of course.

[Hoosier Daddy]

Reading back through this old thread one thing stood out to me...

This one retains abt 2 pumps worth of pressure, after firing.
Pump it 10, thereafter it gets topped-off with 8, in between shots

I thought these were originally recommended 8 pumps max?

[TerryM]

  Eight recommended but ten won't hurt it, especially if the gun is still incrementally building pressure.