www.MG42.us

i wanted to know if you can bolt the rails in the mg42 or not

It has been done. Mainly during setup and initial testing. That said either weld or rivet at the end. A bolt / screw head working it's way "free" and the bolt hitting it would make for a very bad day.
Most folks rivet and it's easy to do and if ever needed resetting the rivets is not hard to do either. A few folks have inserted rivets and then welded the ends making a rivet like bead as they finish. There is at least one other way of welding that oakrodent did and shows how to do on this site also I believe.
Making a pair of jack-screws and doing the rivet job is not hard to do. I believe that the photos are still up and working on how to do this.

Later 42rocker

thanks 42rocker

Robert at RTG International Surplus has rivets, rails and rivet jigs. Good folks to deal with!

Brian at brpguns.com has eails also. If used you might want to check hole placement and readjust the holes in the rails as needed.

Later 42rocker

thanks