Well, as I said I know how 9x19, 7,62x39 and 7,62x54 acts, when fired full auto. I have no personal experience of .45ACP. However here is a good thread about WW2 SMGs and their uses in different armies, by guys who know or have fired those guns, maybe not in WW2 but later.
Presenting again our beloved tanknet:
http://63.99.108.76/forums/index.php...hinegun&st=120
And from personal experince I can guarantee that the Suomi SMG 9x19 was very easy to handle with 6-9 round automatic bursts and regularly landed on target with surprising accuracy, that can not be said from same distance with an AK or finnish M62 7,62x39 on similar full auto bursts.
Also consider this: if you drop one SMG range to 2hexes from three, there will be twenty guys complaining from different reasons that why this gun outranges the other, and have about million arguments why it actually should be the other way round. The developers would probably like to see to drop individual weapon designations and use only a generic SMG, rifle or self-loading rifle or carbine. However this will not happen, because there would be again ten oob makers saying that they want to present their Thompson, M16 or whatever for some reason (reality) to the game, so the individual weapon names will stand.
If you drop all SMGs to range 1hex, SMG-armed formations will suffer heavily. They will be gunned down from 2+ hex range by any regular rifle squad and will be mostly useless in this game system. My opinion comes from 5 years of gaming experience with SPWW2 / SPMBT system.
edited for spelling