I think, but don't quote me...
the list off the top of my head on the European side Aks are Valmet and the Yugos used 1.5/1.6mm receivers from this time frame. Veprs are real recent, throw them in the fray if desired. I do believe all Chinese Type 56 Aks have the heavier RPK style receivers(with exception of the milled variant), and they also usually have slightly heavier barrels.
Some barrel thickness readings..all measured between the gas block and front sight..
MAK-90 milled .615
MAK-90 stamped(both in 7.62 & .223) .608
NHM-91 stamped .668
Egyptian Maadi .580
Romanian typically .584
Polish, Hungarian, Bulgarian, and Russian all seem to fall somewhere within the Maddi/Romanian measurements. But, these nations adhered to strict Russian design.
One or more of those questions is why, extra strength for bayonet use, thought thicker was better for durability or accuracy testing proved it to be a valid point, they were provided a heavy receiver from Russia in the design/planning stage and it just stuck, it's heavier to support the slightly heavier barrel(see above) plus countless other questions, like possible launching of grenades like Yugoslavia or simply make just one receiver and be done. I cant blame "heat treatment" the Chinese are all over this planet, if heat treatment was questionable, they wouldn't have never lived up to their name and hype.
The heaviest x39 barrel I could find was the M72 Yugoslavian RPK, it measures .808 dia at the gas block. Again...I didnt include current Sagias or Veprs. The PSL has a fairly thin barrel for it's 24.5/25 inch length, my example is .592 between the gasblock and front sight, it's two biggest enemies are heat and whip, on a short 16.5 inch barrel rifle it's not as noticeable, but you kick out 10 rds of x54 through that long barrel, quickly, your done till it cools. They are terrible for stringing shots from heat.
And just for giggles, and I will throw this out there.. A while back, and I may have mentioned it at some point, I compared a press fit SKS barrel to the MAK90, other than the length, they measured very close, most measurements were within or even less than .004 of each other at the same respective measuring spots. Maybe they were sharing barrels, I say maybe here very loosely, because it's one example of each, not enough info to even begin pondering. But, logistically speaking, if you could make two weapons systems using a common time consuming part that differs by 4 inches and maybe a bit of final finish machine work, how much production/labor time and material would one save.