I like the idea of limited/realistic ammo, rather than having hicaps and thousands of rounds. So say 30 rounds per magazine, you can carry as many as you want but a realistic limit per mag and you can only reload them at a team "base" (not a respawn point) support weapons would be say 200 rounds/mag, etc.
So even if someone carries 10 mags, that's only 300 rounds, similar/less to a single hicap. If you want to go full auto and empty a whole mag in 2 seconds then you're gonna run out of ammo fast, so you need trigger discipline.
(Maybe i'm biased, my rifle only takes 32 rounds per mag and carrying 6 of them gets heavy fast.)