The only thing I could offer on that is when levelling up the Diamatti’s there were times where the progress I’d made on the gun didn’t properly register until I’d logged off and then signed back in the next day. That was specifically to do with unlocking the Akimbo attachment though so don’t know how applicable it is to your sitch but might be worth keeping an eye on. Sounds unlikely that’s what happened to you guys though. The Supply Run Plunder tactic has been my go-to for levelling up a gun since Warzone launched (or at least since Supply Runs became a thing) so it’s surprising to hear you’re having an issue.
If you’re interested in a detailed analysis of the the two guns a YouTuber called TrueGameData provides a breakdown of the M16 in comparison to the AUG -
- where he argues why the M16 is better. He's basically the go-to for Warzone data so I trust his opinion more than the average YouTuber. That video is slightly out of date because the Cold War guns got a stealth balance in the most recent update which nerfed the 16.3 Titanium Barrel so he's adapted his loadout recommendation for the M16. He now runs it with the Agency Suppressor, Strike Team Barrel, Axial Arms Scope, Bruiser Grip and the 60 Salvo Fast Mag which is explained in this video -
@ 6:45.
He suggests running it with the Mac, which probably makes more sense, but a lot of YouTubers seem to be in love with the FFAR. Gotta say I agree with them - the FFAR feels like it absolutely wrecks people in a way the Mac can’t. It's just the recoil that's funky but you get used to it quick.
A lot of people seem to like the AUG as well so probably worth trying but honestly give that M16 build a go. Takes a while to get used to the burst style but it's deadly if you land a headshot in there. The recoil pattern of the burst also means the shots kick up as you fire so if you aim for the chest with the first bullet the chances are the second or third will naturally hit the head. if you do hit the head it's game over for them. Only a gun to be used at mid-long range though, too slow at closer ranges - that's where the FFAR takes over. Apologies if this is too much info but I basically did the same breakdown for one of my mates earlier tonight so the information is all still fresh in my mind.