Another thought that might influence you. Barrel replacement, on many open bolt SMGs the barrel removal is very easy and can be changed out even at the range by a nub but other guns will require an armorer with specialized tooling. Unfortunately, many people will get a squib in there SMG that will cycle the action and will have a bulged barrel soon afterwards. When this happens on a MP5 or Thompson you will need a trained SMG smith to replace it. On a Sten, Swedish K, Uzi etc. you just unscrew the barrel nut and swap the barrel out.

