some times you can put a USGI green follower in a "iffy" mag and get it to run. sometimes that don't work either.
nose diving rounds ain't a good sign for reliability and plastic mags that are a bit wobbly in the feed lips are prone to double-feed too.
m4 feed ramps are one of those things where if you NEED them --something is up with the mag-- my guess would be the location of the mag catch is too low on the mag--
mags vary too and the low dollar one have the most 'play" in where the critical stuff goes.