I keep hearing about new 22mag ammo and trading because it won't work in someones rifle.
I have a marlin model 57 lever i bout in 1969, used it a lot for years but haven't fired it in 20 years.
Is new ammo going to be a problem, or gun to gun problem?

I haven't heard anything like that, and a search didn't turn anything up. I have a 1980 era H&R 700 and recently shot some Armscor, two diff CCI loads, and another brand through it with no problem. What issues did you hear reported?

I haven't heard of any problems with 22mag ammo other than the Keltec handgun not cycling well with the ammo using 30gr bullets, and hear that pretty often.

That Marlin 57 is a sweet rifle, had one stolen from my truck about 25 years ago.

maybe i was hearing about the keltec problem.
the 57 is nice, first thing that got my attention was if you open it up enough to see if round is in chamber you might as well kick it out, not going to close back up.
going to find some kind of scope for it, "it didn't need one 20-25 years ago"