Anthony G. Williams has updated and expanded his history of Assault Rifles And Their Ammunition. Tony knows more about cartridges than anyone else I know and I doubt that there are many people who have fired more types of assault rifles than he has.
Attempts to improve the power and range of the SMGs, such as the development of the .45 Remington-Thomson in the experimental Model 1923 Thompson SMG (which used a very powerful loading developing almost three times the muzzle energy of the .45 Auto) and the use of the 9×25 Mauser round in the 1930s Solothurn S1-100 and Hungarian Kiraly 39M and 43M SMGs (which saw some service), did not catch on. There is a limit to the degree to which the performance of such weapons can be increased as their large-calibre, relatively light and round-nosed bullets lose velocity quickly. Also, the basic API blowback system used by most SMGs is not suited to high-powered ammunition, although the Kiraly and Thompson M1923 had more sophisticated mechanisms.
( Assault Rifles are defined as “military rifle, capable of controlled, fully-automatic fire from the shoulder, with an effective range of at least 300 metres” )