Your 7.62 will shoot the steel to doll rags in short order at close range.
Next the steel when badly cratered splatters back even if angled.
Cardboard silhouettes may be a better option for the rifle.
We shoot 2 and 3 gun matches at our Club. We have a a Rimfire Division in the 2 Gun. Lots of AR-22's in use, as well as the 1911-22's. I shoot both rimfire and centerfire AR15's. I totally disagree about the 22 not being a good training tool. I also shoot a 442 and have an LCR 22 for practice. You can shoot up a brick of 22 for $20. You can get in some serious trigger time for your money spent. I find the trigger time with a 22 out weighes any similarity of recoil concerns.