Deleted member 1487
It would be interesting to wonder if people might have moved toward a smaller caliber to lower recoil and get performance for 1000m or less range, rather than a bigger, heavier round for 2-4km range (when indirect MG fire was en vogue).The BAR was a great addition when it was just the M1903, it showed the way much like the Chauchat how suppressive fire opened up Squad tactics to fire and movement. The BREN and MG42 show how to get this done and would have been even more devastating had either army paired it with a Garand or MAS-40 equivalent but perhaps the success of them let us linger with bolt-actions longer. I do not think we need the StG or its progeny to see that the path was certainly towards a SLR that mostly fired semi-auto with option to full-auto paired with a LMG and either rifle grenades or M79 launcher as the pattern that likely sticks. Again the push would be to concentrate the LMGs at Platoon rather than distrubute them once you have such rifles, but that is no certainty. The assault rifle might only get developed once armies move to full APC and then IFV theories, that lets us remove the LMG and use the dismount infantry to be the maneuver element as the APC/IFV acts as the fire base. The Soviets seem to have showed us that was the theory once you build a BMP. Thus the StG/AK47 is a product of the next generation after the Garand/FAL/CETME serves out the 1940s to 1960s era. If you asked how things go without a war that is my bet. Before 1950 I think everyone has a Garand equivalent or even the FAL capable full-auto like rifle in service or tracked to enter service, SMGs fade and the GPMG retreats to a more traditional fire support role.
Stan Crist makes an interesting case why we should adopt a 6mm universal round now.
Given that the US experimented with the 6mm high velocity round in the late 1890s it is possible you could see a shift down in calibers to moderate recoil and get practical infantry weapon rounds for SLRs without going full intermediate cartridge assault rifle.
So a 6-7mm battle rifle might well be doable, with it having a full auto mode for "LMG" role as needed.