[Drake]

In milsim games, the main difference between support weapons and regular guns is the ammo capacity (assault rifles usually being restricted to lowcap or realcap mags and LMGs being allowed to use box mags).

The IAR is fed from regular 30 round mags: if your intention is to use a hicap and run it like it was some belt fed weapon, that's patently unrealistic and goes against the very spirit of milsim. However, if the game is running real cap for everyone and you were using 30 round mags, I could see you being allowed to carry extra mags for the IAR; you'd still be carrying less overall than other LMGs -- typically the Automatic Rifleman carries about twice as many mags as riflemen, but most real cap milsim games allow between 500-1000 rounds for LMGs. And it would really come down to the organizer.

It's important to keep in mind the IAR -- Infantry Automatic Rifle -- is just that: it's not intended as a bona fide support weapon but as a more maneuverable automatic rifle. Keep in mind that USMC doctrine had one M249 per fire team (the automatic rifleman position), that's 3 LMGs per rifle squad (or 9 per platoon), arguably overkill. So a number of them are being replaced with the lighter, more maneuverable M27.



Also, if you want to get really technical about realism and realism, the IAR has a more limited ability to lay down large volumes of suppressive fire due to it having a fixed barrel -- meaning the barrel can and will overheat, and unlike real support weapons there's no way to swap the barrel.