Magazines are the #1 cause of malfunctions. Use the ones you trust the most, and realize they are the weak link in the design. It was build to use a straight 20 round mag, nearly new every time. Treat M16 mags like the flimsy lightweight disposable throw aways they are, and don't stress over crushing a bad one.
Ammo is the #2 cause of malfunctions, and tightly controlled by milspec to provide adequate gas to operate the M16/M4 in a narrow window. The military doesn't issue plinker rounds, or odd ball weights. It's a select and narrow range. Run it on full power rounds, it works. Not everyone gets good results with cheap import fodder, reject surplus overruns, or anonymous reloads from a gun show. Those are almost universally reported as part of a kaboom or function problem.
It's always amazed me how many will argue milspec guns are the only proper standard, then shoot junk fodder in them and claim great accuracy from three shot groups. Military standard is milspec issue ammo only, and ten shot groups accepting the lot. That draws a distinct line in the sand for those who are really only giving it lip service.
