Crossman .22 Nitro piston

[Jerry_NJ]

Forget the model, simple facts:  8 year old .22 Crosman nitro, never tuned, low mileage (pelleage), kept dry but in garage and never "professionally" cleaned.  Problem, shooting at beer cans at about 30 feet, I find after about 5 shots the pellets start to drop at least 2" at said distance, temperature about 40 degrees. This has happened on several occasions.  Is there anything less that a tuning done properly that might fix the problem?

[Airspace]

Either you need to replace the piston seal or you may need a new piston, both which are available from Crosman. If it's the piston order a new seal with. They may come with one not sure about that.

[Roadworthy]

You didn't define "tuning" so you can do some troubleshooting.  After loading and closing the gun lay a tissue over the breech.  When you fire the gun it should stay put.  If it blows away your breech seal is bad.  That's probably not the problem but it's a starting point and an easy fix.
To go deeper you will need a bar clamp or spring compressor because the piston seal and the gas spring (Nitro Piston) are both internal parts.  Based on my experience with Crosman my guess is the piston seal.
If you order a piston seal you may wish to order a spare breech seal at the same time.  These are not difficult guns to work on but you do need the proper tools to do so safely.

[Privateer]

8 years old? I'd order a new piston and seal.
I did a tune on one a few years back and not long after returning the gun the piston failed.
I payed shipping back to me, paid for and put a new piston in, and payed shipping back.
Were I to do another for anyone? A new piston is a must!

[Jerry_NJ]

Thanks all, and Roadworthy I recall having some problems closing the breech, and that may be accompanied with some general leakage. I'll try the tissue test for a start.

Now I have a Ruger springer and Crosman nitro needed a real repair after less than, I'll guess 2,000 shots each.  Well neither of them was expensive, don't recall but guess $200 and $300 respectively.  I guess even the higher priced guns benefit from a good after manufacture tune-up/tuning.  Maybe the most reliable gun I own is an even less costly (what $100) a Crosman C02 with a 12 shot magazine.  Last time I was "here" it was to get help on the Ruger.  Roadworthy did a great job, now all I have to do is carry out the advice.  You guys/folks do a great job. Thanks,