Fixing Air Guns

[n2ize]

Hi. I have an old air gun from when I was a youth. It's an old crosman pump style air gun that fires BB's and pellets. I remeber I got it back in 1974 and it lasted me for many decades. The model number is the 760. A few months ago I dug it out of the closet but found that unfortunately it doesn't hold compression\. You can pump it but the air leaks out as fast as it goes in. Most likely the old O-rings and seals are rotted away. Nonetheless I would like to fix it for nostalgia if nothing else.

I noticed the crosman is still in business and they still have the owners manuals, diagrams, exploded views and some parts. So assuming I can get the parts I can probably order the parts I need. What I am not sure of is that once I get it all apart if I'll ever get it back together right. Has anyone out here fixed these things. I'd imagine it can be done, but I am not sure how much of a headache it will turn into....

[KG4CGC]

Just buy a new one.

[n2ize]

Just buy a new one.

Yeah, I have thought of that. But the whole idea is that I had this gun as a kid and it brings back memories. I got it back in 1974 so it's near 40 years old and has a lot of fond memories. I would like to get it functioning again.

[W5GA]

John, airguns are pretty simple devices. The seal that's leaking is likely leather...a good oil bath (NOT WD-40) may make it better without disassembly. If not, you can send it to me and I'll get it going for you.

[n2ize]

John, airguns are pretty simple devices. The seal that's leaking is likely leather...a good oil bath (NOT WD-40) may make it better without disassembly. If not, you can send it to me and I'll get it going for you.

Interesting. What type of oil would you recommend ? Crossman sold an oil for their air guns called "Pellgun Oil" which was a light silicone based oil. They used to tell us not to use petroleum, only silicone based oils. I appreciate the offer, if the oil doesn't work and if you are not too busy I'll be glad to send it to you for repairs. Of course I will pay you for parts, labour, shipping, etc. It's a nice gun.I used to shoot .22 cal match rifles when i was on the rifle team at my high school. When i was home I couldn't use my .22 so i would practice with the air rifle, using the regular US Army 50 ft. small bore rifle targets we used in the matches. That air rifle helped my marksmanship skills a lot. Those were some fun times.

[W5GA]

Interesting. What type of oil would you recommend ? Crossman sold an oil for their air guns called "Pellgun Oil" which was a light silicone based oil. They used to tell us not to use petroleum, only silicone based oils. I appreciate the offer, if the oil doesn't work and if you are not too busy I'll be glad to send it to you for repairs. Of course I will pay you for parts, labour, shipping, etc. It's a nice gun.I used to shoot .22 cal match rifles when i was on the rifle team at my high school. When i was home I couldn't use my .22 so i would practice with the air rifle, using the regular US Army 50 ft. small bore rifle targets we used in the matches. That air rifle helped my marksmanship skills a lot. Those were some fun times.

I'd use the Crossman oil. The reason they say to not use petroleum based oils is because it will rot leather. If you can find a silicon oil cheaper than theirs, then use that. Give me a shout if that doesn't work, and we'll work something out.
Just had a thought...if the Crossman oil isn't available, try these guys http://hambydairysupply.com
They sell an oil that works on leather seals.

[n2ize]

I'd use the Crossman oil. The reason they say to not use petroleum based oils is because it will rot leather. If you can find a silicon oil cheaper than theirs, then use that. Give me a shout if that doesn't work, and we'll work something out.
Just had a thought...if the Crossman oil isn't available, try these guys http://hambydairysupply.com
They sell an oil that works on leather seals.

Thanks. I'll check it out and give it a try. The oil might just do the trick. I'll let you know.

[N8YX]

The old 760 is a far better air rifle than the new 760. Your best bet is to repair it.

Something to consider when restoring them is the material used in the o-rings. This is a huge bugaboo with a CO2-powered unit. I've seen the o-rings harden in the cold and refuse to seal after a few shots, and this leads to excessive gas leakage...which in turn greatly exacerbates the problem and results in rapid cylinder depletion.

If the cycle time between shots is low, a pneumatic gun may experience similar issues. Select o-rings made of material which stays flexible to 0 degrees.

[n2ize]

The old 760 is a far better air rifle than the new 760. Your best bet is to repair it.

Something to consider when restoring them is the material used in the o-rings. This is a huge bugaboo with a CO2-powered unit. I've seen the o-rings harden in the cold and refuse to seal after a few shots, and this leads to excessive gas leakage...which in turn greatly exacerbates the problem and results in rapid cylinder depletion.

If the cycle time between shots is low, a pneumatic gun may experience similar issues. Select o-rings made of material which stays flexible to 0 degrees.

A friend of mine had a Daisy CO2 pistol that did exactly that. Particularly in cold weather. We'd put a new cylinder in. The first few shots were fine then it would start pissing out CO2. One time it even spit out a bunch of BB's along with it. If you let it warm up for a while and put in a new cylinder it would be good again.

My main issue with CO2 guns were the power. First few shots were excellent. Then as the cylinder pressure went down you'd get a whole lot of mediocre low power shots. I prefered the pneumatics. It took longer to pump them between shots but at least power levels were consistant from shot to shot. Plus, CO2 cylinders were getting more and more expensive.

[WØTKX]

Doug is a great resource, but you might be able to fix it yourself.

A little Google-Fu came up with this...

Depending on the age of your gun, here are Parts Diagrams straight from Crosman. You just need to determine the approximate year it was made. As in my answer to your last question, you can try to find the gun that is yours by comparing features to this list of other 760's.

Model 760 Powermaster starts half way down the list.

Year List - http://www.crosman.com/airguns/service/d…

Parts Diagrams
1966-1977 - http://www.crosman.com/pdf/manuals/C760S…

1977-1980 - http://www.crosman.com/pdf/manuals/C760-…

1980-1983 - http://www.crosman.com/pdf/manuals/C760-…

1983-2001 - http://www.crosman.com/pdf/manuals/C760-…