Those 100 round mags ever jam?
It’s a 2009 Beta Mag ($300), and I lubed it before ever using with graphite from the provided kit/carrying case, and it fed like a hose. Cleaned it every other mag load thru. Never a jam for me, in the 5x I used it.
It was heavy as an anvil, full load of ammo, so I switched to the Surefire 60rnd mags from Brownells:
http://www.surefire.com/tactical-equipment/high-capacity-magazines/mag5-60.html
What a sweet mag.