Benjamin 312 w/leather pump cup

[Wunderwerks]

Broke this one down and was surprised to find a leather pump cup.  I doubt if anyone makes a replacement leather cup so the entire pump head will probably need to be replaced.  It had no compression so I'm going through the valve assembly also.  There is no SN on the gun so the mfg. date is unknown.   I just found the leather assembly interesting so I thought I'd post a picture

[TerryM]

  I pulled one of those out of a 317.  Found a new leather seal from JG but couldn't get it to work right.  Ended up replacing with a newer, rubber cup.  Did the same thing with a Crosman 102 a few years ago.

[Wunderwerks]

Terry,
Were you able to replace just the cup or did you replace the whole piston head?

[TerryM]

  I used a non-adjustable piston from a newer 392/397.  I built up the cup with silicon caulk, increasing the overall length very slightly and filled the concavity of the cup so it would mate better with the flat valve face in the 317.  So far, it's worked well.

[happymecanic]

Broke this one down and was surprised to find a leather pump cup.  I doubt if anyone makes a replacement leather cup so the entire pump head will probably need to be replaced.  It had no compression so I'm going through the valve assembly also.  There is no SN on the gun so the mfg. date is unknown.   I just found the leather assembly interesting so I thought I'd post a picture

Hi Rich,

IIRC Benjamin started to use the Hicar seal (synthetic) in 1950, so yours shall be a '49 or earlier. HTH.

[thwakk]

You might try a variation of an "alcohol flush" that may revive the leather seal.

https://www.tapatalk.com/groups/americanvintageairguns/alcohol-flush-for-pneumatic-ag-s-t8861.html

[TerryM]

  Rich, here is a link to the thread I started a year ago, it shows how a made the newer piston work.  https://www.gatewaytoairguns.org/GTA/index.php?topic=191537.0

[Hoosier Daddy]

Hi Rich,

IIRC Benjamin started to use the Hicar seal (synthetic) in 1950, so yours shall be a '49 or earlier. HTH.

My 312 had the predecessor to the Hi-Car seal and it was rock hard rubber, a call to Rick at Precision pellet confirmed it was an early one, possibly pre-war. (part 3151 in the attached diagram)
He set me up with the Hi-car seal and cup.... easy swap.

If yours is leather it should be earlier yet!!!
I would soak it in Neats-Foot oil and see if it is salvageable.

[TerryM]

  I don't think I'll try to replace any more leather pump cups.  There's a reason they switched from leather to rubber.

[happymecanic]

Hi Rich,

IIRC Benjamin started to use the Hicar seal (synthetic) in 1950, so yours shall be a '49 or earlier. HTH.

My 312 had the predecessor to the Hi-Car seal and it was rock hard rubber, a call to Rick at Precision pellet confirmed it was an early one, possibly pre-war. (part 3151 in the attached diagram)
He set me up with the Hi-car seal and cup.... easy swap.

If yours is leather it should be earlier yet!!!
I would soak it in Neats-Foot oil and see if it is salvageable.

Thanks for straightening that up Scott.