Quite the thread....it won't die and covers a multitude of ideas! It has been quite some time since I've been on WW2AC, I remember this thread when I last dropped in.
I find it interesting that the US Army would not change from .30-06 to .276 for the Garand yet come up with an entirely new round AND weapon, and make some 6.2 million of them. Talking about the M1 Carbine family.
re not changing to .276 for the Garand
When a new rifle comes on line, it may take years to change over all the units. Pre-WW2, not a huge problem because the US Army was small yet the units were scattered all over the place. Plenty of Springfields around, all the Machineguns around....so from a logistics point of view, perhaps a good decision. Then the build-ups....1940-onward
From the operator/capability point of view, another matter. For the larger, more powerful round, the Garand had to be larger and with that the weight penalty. Quite the beast of a weapon as it was yet a smaller/lighter version with a shorter action would allow more rounds in the weapon and on the person of the soldier. Perhaps an opportunity missed.
My US Cavalry career, M16/M4 family of weapons. I carried 210 rounds (way more than a WW2 load) with more in my ruck in magazines. This in addition to WATER (lots), some food in the pockets, body armor, helmet, grenades, commo gear. Are 210 rounds really needed? Well, rounds left in the FOB are like planes needing altitude and airspeed to fly, lack of either can be a problem.
OK, now for the M1 Carbine
Battle Rifle? No. Compared to a Garand, range and put-down power, the carbine falls short. But that is apples and oranges comparison. Compare the carbine to rightly to pistols and SMGs, what it was designed to replace, and it is a whole new sheriff in town. Pistols, a 25m shot is max. SMGs, rated at 200m. Hmmmmm, suppression maybe. I'd say 100m against a team and maybe 50m vs a point target like a head poking out around a building corner. Deadly at 25m. The M1 Carbine was designed as a Personal Defensive Weapon (PDW) around a rather dubious cartridge with the goal of providing NON-RIFLEMEN and CREW-SERVED WEAPONS, Drivers, Signalers, Artillerymen etc something easier to use and more effective than a pistol. Then-Current SMGs were in the 10 pound range. So the "Ass and Trash" as the line troops calls everybody else got the Carbine, lots of them. Stated range of 300 yards shots would actually be random for all but the most practiced, reasonable accuracy at 250, good results at 200yds. (I hate using yards but that is how things were then)
Way more punch with the .30 cal Carbine round compared to SMG ammo and far better down range ballistics.
Carbine is easier to shoot than a pistol
Light weight, low recoil, self loading, high capacity magazine means you get your weapon to your eye faster, your shot does not upset your aim, reloading is taken care of so your sight picture does not change, and 15 rounds means it is not a big deal if you need to fire another round to get the job done. I cannot imagine situation like the Battle of the Bulge where small clusters of non-Infantry; clerks, service and support troops, cannoneers sans the big guns, truck drivers etc plugged gaps, manned outposts and road blocks. I'd imagine the volume of fire a squad of pissed-off soldiers with Carbines could lay down and the lethality at 200m and below would sound like a far greater force.
An opportunity missed here. With a new Carbine cartridge anyway, no need in my judgement to keep .30 cal other then using existing boring and rifling machine bits.....a somewhat hotter round in the same overall length, necked-down case...would have pushed the effective range out to 300m and greater. I'll leave the bullet diameter and weight to others. This would have pushed the M2 select fire carbine from being a PDW into being an Assault Rifle.
STG44. BIG and HEAVY. Yet this worked....moderate recoil so the sight picture would remain solid for a second shot at rifle ranges and still good effect with short bursts. IN this regard, the lower RoF and greater weight make this more controllable, a better killer than the AK family. Plenty of STGs were made. My looking into this shows that they tended to be issued to units in quantity rather than piecemeal. This gives greater effect and somewhat eases the ammo supply burden. This is to say going to specific units rather than front-wide penny packets.
Ammo production was slow ramping up to the goal of 1000 rds/wpn/month.
STG45. YES! Alas, too late. Far too late.