Don't have the M10, but have a WASR which uses the same receiver with welded inserts instead of dimples. Mine has a little mag wobblem but so do the AK clones with dimples that I've had. Not too severe in any of them. No problems with any of them either as far as feeding goes.
I have seen a couple of remedies on youtube. One involved compresing the receiver (didn't seem like a great idea to me. The other involved using JB Weld in the area of the welded inserts, then filing it down to get a good fit with the mag.