I agree that the modern intermediate cartridge assault rifle has made the sub-machine gun mostly obsolete. But I see the old attitudes are still alive and well. Their only disadvantage was the lower power of the cartridge. True, they were heavy but so are most assault rifles, including an M4 carbine with all the gadgets attached. In comparison, an M1 carbine is quite light. Please note that I am not calling an M1 carbine either a submachine gun or assault rifle; only that it is relatively light.
How are submachine guns "harder to keep fed?"
And Mr. James K, volley fire was aimed fire. That's why those old rifles had sights that went up to high ranges. Volley fire is not indirect fire.
Shoot low, sheriff. They're riding Shetlands!
Underneath the starry flag, civilize 'em with a Krag,
and return us to our own beloved homes!
Buy War Bonds.