OT air gun question

[Steven Martin]

Hi Guys, I'm not sure where to ask this question but I'll bet someone here knows. I have an old Benjamin pump up air rifle that will hold air but will only release or portion out small amounts at a time. I can get 3 shots out of 3 to 5 pumps and they are weak shots. I thought the hammer spring might be weak but it's as stout to cock as my other pump ups. Any thoughts or advise where to ask? TIA, Steve

[John Sukey]

Souds like the seals are leaking.

[phil441]

If it hasn't been oiled in a number of years you can bet it's the seals.
I had my Crosman pistol overhauled a few years ago and the smith reminded me what that little opening at the cocker hinge was for. The opening next to the little sticker saying to oil every 250 shots......oops!

[JB White]

There's a special T-handled wrench with a hollowed square head used to remove the piston to be able to change the seals. Unless you plan on working on a lot of Benjamin/Sheridan air guns you're probably doing better by letting a service center perform the task. The cost of the wrench and the retail cost of the parts would work out to be close to the same. Learned that a good number of years ago while working on paintball guns based on those.
First I would try air gun oil just to see if the seals will swell. If it doesn't come back to life in a couple of days then bring it in for an overhaul.

[Liam]

In reference to "oil." I have an RWS Diana model and it has kept my deck, etc. clear of chipmunks for years. I have yet to oil it, although I do recall that the instructions STRESSED to NOT use a petroleum product. Regular machine oil will actually break down the seals. There exists special, plant-derived oils specially formulated for the lubrication of such air gun seals. Although I never owned a high-end Beeman air gun (darn it!), I have purchased accessories from their website. HTH

[da gimp]

Ya wanna talk High end air guns? Look at the Anschutz .177 match rifles, they cost more than the Annie .22LR guns, @ about $2000 or more. But a dern good shot can shoot aspirin sized groups for ever with them.

da gimp

[JB White]

Another thing to watch for are some synthetic oils used for firearms. While they don't have a petroleum base they do contain solvents which will eat the seals alive. Birchwood Casey offers a synthetic they claimed was safe for pneumatic guns but it isn't.

Crossman Pellgun Oil is available at most chain sporting goods stores and sporting goods departments. Not the "absolute best" product being hawked on the market but it does work.

[Steven Martin]

Thanks guys! My question was confusing and I apologize. My problem isn't bleed down from bad seals, the thing will pump up just dandy and stay pressurised for days. The problem is, once it is pumped up (3-5 pumps), I can then shoot 3 or more times with it but each shot is weak. It's sort of like the pressure chamber is stingy, metering out only a fraction of the power it should each time. BTW, it's a model 312.

[phil441]

I should have mentioned that you should never use a petroleum based oil!
Most air guns are not designed to hold an active air charge for any extended length of time.
My guess is that when you finally do take it to an air gun Smith (recommended) he or she will find a small piece of seal in the metering orifice.

Keep us posted.

[da gimp]

I'd never known about not using petroleum based oils in air guns. This ain't a smart a$$ed question, but serious inquiry, could you use a canola oil,soybean oil or corn oil in an air gun, or is this being too cheap & silly? Not sure if I've ever seen an oil in our local stores made just for use in airguns.

da gimp

[JB White]

I'd never known about not using petroleum based oils in air guns. This ain't a smart a$$ed question, but serious inquiry, could you use a canola oil,soybean oil or corn oil in an air gun, or is this being too cheap & silly? Not sure if I've ever seen an oil in our local stores made just for use in airguns.

da gimp

Vegetable oils go rancid and gum up after a while. That's why they shouldn't be used for oiling natural finish wood butcher blocks and cutting boards. Someday remind me to tell you about the time I had to work in rancid corn oil while changing out the screw conveyors in a corn processing plant. BTW, it's flammable too.

You should be able to find air gun oil anywhere that sells air guns. Walmart, Kmart etc. wherever they have the BB's pellets and paintballs. You may have to ask for it.

[da gimp]

did a clean up on huge soy oil tanks years ago in KC,Mo. so that they could be inspected & if necessary rebuilt like Ken the K does. Squeegees were invaluable, vactor trucks too.

The remaining soy oil wasn't rancid, but we durn sure had fun cleaning it to perfection so the scaffold could be built for the inspectors., as the access door was too small to bring in a Genie lift or scissor lift.

We've got two of the old maple butcher blocks, they weigh about 350 lbs, clean em with hot soap & water, rinsed clean , then chlorox sprayed, then oil. 1 was my parents & the other I picked up @ a lodge bro's sale, both are about waist high.

I'll look for the air rifle oil JB, TY.

da gimp