Finally, a topic I actually have some experience with.
I picked up a couple extra factory mags off gunbroker.com, plus an (apparently) modified AK mag. The modified AK mag required no modifications to my carbine; however there is a very slight "looseness" to the fit. I've run about only 90 rounds thru it but no FTF so far.
Of course, no problems so far with the factory mags either.
Steve
Madison, WI