I need to find the pump seal for a Benjamin franklin model 312 air rifle. Where can I find one.

Try google

Reseal Repair Seal Kit for Benjamin 340 342 347 Air Rifles eBay

Benjamin 342 22 seal repairs Airguns Guns Forum

Benjamin pellet gun repair advice help needed

Even though the full name stamped on the pump barrel jokingly referes to our first president, the name "franklin" doesn't have any thing to do with either the company's founder, nor any other direct connection...I believe that it was more of a company ruse to associate the Company's name with an American PATRIOTIC figure. Benjamin is actually the founders last name...simply put, that is nothing more than my personal opinion...bottom line; the name franklin refers to absolutely nothing, maybe the name of Benjamin Franklin wasn't trade marked at the time it was first used!!

why to check benyamin franklin meaning?

pyramidair.com has a seal kit. it also comes with a diagram. Benjamin and Sheridan air rifles do not have springs to propel the pellet. also never use vasalin. specifically for a Benjamin or Sheridan you need to use pelgun oil (also found at pyramideair.com). use pelgun oil because it is a non detergent fossil compound) the main intention is to condition the seals every 250 rounds. never use silicon based lube for this gun specifically. silicone lube is for spring air rifles such as break barrels.

I"ve had Alan Schweitzer work on my Benji 310. Great work and very reasonable.
http://www.abairgun.com/

http://www.crosman.com/airguns/service/repair

I couldn't find the model 317, But crosman bought benjamin, sheridan. Check it out.

Springs tend to loose their performance after a few years is air rifles. Check also the seal/o rings on the piston rod and the blow hole. I found waxing it with Vaseline makes it last longer and seals more.

I recently purchased a rebuild kit for my 342. I bought the kit from airgundepot. It was the kit for the
392 and I modified it a little. On the new plunger, you have to drill a hole in the center of it the same
size as the pin's smallest diameter. You can use all of the parts in this kit except for the small o-ring. I think it sold for about 39 dollars or so. My rifle was manufactured in 1972 and it fires like new.