The M27/38 is a headache. It’s not an LMG the marines don’t even issue it with a high capacity magazine.
It’s as heavy as the XM7 despite being an assault rifle and not a battle rifle. With the VCOG now the marines standard issue the M38 pretty much doesn’t exist. As the NGSW proliferation into the U.S. Army goes ahead it’s probable that the M27 will follow the M38 into the history books. With XM250 taking the IAR role as it was designed to in the Army and XM7 takes the rifle and DMR roles.
The USMC call the M27 an Infantry Automatic rifle, what they got was basically an M4A1 with a Piston system, heavy barrel, funky rail system and bunch of proprietary parts. They then back doored it into an infantry rifle. The main reason they did this was urban fighting where the Marines wanted selective fire to allow the squad gunners to have a rifle better suited to close quarters cleaning. They also wanted them to operate as accurately as the rest of the squad so semi automatic fire.
In Magazine vs belt. A box magazine is generally less likely to jam so long as it’s a well designed magazine in good repair vs a belt that can get debris trapped in it. However a drum is the worst of both worlds.
Yeah, my example for the M27 and M38 is exactly that the whole "DMR" and "IAR/LSW" thing can be fuzzy depending on modern attachments, and that is the case for QBU-191 (which in some ways is a spiritual analogue to M27/38).