Yeah, you can peen steel with a brass punch! Don't ask me how I know.
Just go to Harbor Freight and pick up a bench-top press. I think mine is rated for 1,000lbs or less. It's pretty cheap. That's all you need and you'll find lots of uses for it.
Just from my experience and conversations with other MM owners, the .223 MMs seem to be about 3/4 to 1 1/2 MOA shooters. Not benchrest, but certainly not bad for such a little dainty.
Mine is an Interarms import. It has a NATO-type chamber and a 12 twist barrel.
