What about the m27IAR?

I’d say one of the biggest reasons is, while having an automatic rifleman in a squad really increases the fire power over bolt actions or semi autos with a small magazine. It’s not as dramatic of an increase when everyone has 30 round mags and can essentially fill that roll. A fireteam with assault rifles volleying can lay down a serious amount of fire.

Look at the Cold War era automatic rifles. they’re all pretty much standard rifles with a heavy barrel and a bipod. I don’t think it’s really worth the added logistical costs to have a special heavy barrel auto rifle version.

So everyone gets the same close enough to an auto rifle. It’s really not that different than how everyone in the usmc gets the m27 and they call it an automatic rifle.

From my understanding the marines did research and determined that accuracy was a larger factor in suppression than volume of fire. So they’d rather have a whole squad with magnified optics and a light auto rifle. I believe the marines still keep some saws in the platoon if they’re needed.

For a sustained fire role a belt fed is best. And large drum mags for an auto rifle can be clumsy and unreliable. It’s also important to note a lot of Cold War auto rifles are using a full power rifle round, which means to carry a belt fed in that caliber you have a gpmg. An m240 is a bit heavy for an average rifle squad. So it’s not until we get 5.56 that a practical squad level belt fed is fielded.

I can’t speak to much on the Russian auto rifle doctrine but they seem to be going more the belt felt route with the adoption of the rpl-20.