In this case comparing Sten and MP5 would be very much case of apples and oranges even if the both weapons are 9 mm x 19 caliber submachine guns. Like most of World War 2 submachine guns Sten is based to simple blowback and fires from open bolt - hence it has heavy bolt and strong recoil spring. MP5 on the other hand is gas-action weapon that fires from closed bolt and has roller-delayed bolt. Due to its operating principle from these two Sten is much more effected to type of 9 mm x 19 ammunition - in less extreme cases the effect is shown in changes of theoretical rate of fire.Poot wrote:Sid,
What's interesting is that up until the time we used rifles (AR15) across our entire entry element, most personnel used MP-5s loaded with 147 grain pistol ammunition, the same ammunition that was used in the pistols themselves. I think by then they had reached the 'sweet spot' of the loading and powder combination with a load that would accommodate/cycle in both weapons systems.
As for having separate pistol ammo and submachine gun 9 mm x 19 ammo - number of countries apparently did that. Here domestic industry concentrated making submachinegun ammo, which had 115-grain bullets & was loaded as hot as possible - pushing muzzle velocity to around 400 meters/second. Pistol ammo in this caliber was imported and typically had 128-grain bullets & was loaded to level of about 300 meters/second.