Shooting my 783 Marlin .22mag today that I bought new in 1990. Never had a problem but today the case didn't come out of the chamber after I opened the bolt. I got a cleaning rod and pushed it out. The case split or cracked lengh ways. It's the same winchester ammo I use all the time. The gun has about 2,000 rounds through it with no problems. Any help would be great.

Do you think it may have been a bad shell from the factory? Did it seem any different when you shot it?

How long has it been since you cleaned her? It very well just could have been the ammo but I find that the less I clean my rimfires, the more malfuntions I see. Rimfire ammo is so dirty it isn't even funny. The chamber gets powder fouled as will the action, the trigger mechanism and of course the barrel. Try a good powder/lead solvent and run a few patches soaked in it till the patches START to lighten up. Then run a soaked patch and just let it it for at least 30 minutes and then run your brushes through the barrel and a swab through the chamber. I find that rimefires always seem to take a little longer to clean than their generally cleaner firing centerfire kin.

I'm agreeing with MJY. I'd spray some copper cleaning "stuff" in the chamber and just let it work in there for a few hours. (Of course, I'd do the same with the barrel, but it's probably the chamber that's giving you the pressure issue)

Then scrub it out real good with a copper brush soaked in your favorite solvent, followed by a half-a-dozen patches, followed by another copper brush of your favorite solvent, followed by enough patches to soak up the solvent.

That should get you back to "normal".

You would be suprised at the amount of stuff that can
build up around and under the extractor of a 22 rifle.
I think this should be an easy fix.

Thanks, I'll give it a good scrubbing.