Most reliable electric box magazine

[Muppetdaze]

Anyone got any hints?

Currently using a star compatible hong-kong thing on my star m249, a stock A&K M60 box mag and seen countless other types

Am looking to build something a bit different but am looking for the most reliable/forgiving feeding box mag so would love to hear input

or even the easiest electric mag to cut about?( not joking, I'd love to get an M2 built using a real ammo can as a mag , 20k rounds ?)

realistically it has to be 2500 rounds plus

what I'm building will probably be side feeding or if I get too excited about the M2 instead it may be feeding from anywhere