pounce, gun wonks!
Naw, it’s too easy.
I have no idea.
I would WAG the latter, else the Sten would presumably have used .45 as well if only to take advantage of existing munitions factories and stockpiles.
That being said, since the Sten was not only designed for British use but also with air drops on partisans and resistance members across Europe in mind, the choice to use the ubiquitous 9mm Parabellum bullet could have justified itself either way. Every European military used 9x19mm to some extent or could raid some off the Germans and Italians in the worst case scenario, but .45 ACP wasn’t that widespread if I’m not mistaken.
The 9mm Parabellum was also one of the few pistol rounds which was proven to work reliably in automatic weapons, and the Brits were already manufacturing/issuing it because of their use of the Lanchester SMG, which was an exact copy of the German MP28.
One time I was watching a WWII film with my father (as a WWII vet he hated to watch WWII films - he thought they were all stupidly done), and it showed a grunt wearing a shoulder holster rig. He said, “He must have owned a Samurai sword.” I questioned this and he explained that many soldiers and marines would trade the sword (often made by Seebees) to navy and marine fliers for the pistols and holsters issued to them. At least in the Pacific theater of operations combat units were not exactly picky about ordinance of the ground pounders. My father also said that another group issued the shoulder holsters rigs were official jeep drivers.
The BAR had some significant problems. Its greatest failing is that it does not have a quick-detach barrel. Guns like the Bren could be fired at a much higher rate with the barrels switched out for cooling. If an individual barrel burned out, it could be discarded and replaced easily in the field. A burned up BAR had to be repaired at the armory level. A second failing lay in the magazines. BAR magazines had notoriously weak springs and SOP was that they were to be loaded immediately before use. Letting them remain loaded for any length of time caused the springs to take a set and resulted in feed problems. The BAR was also known to have extractor problems, which while it could be replaced by the user, wasn’t something you wanted to be doing in combat. There are other criticisms, too. The BAR was “too accurate” which is to say that it didn’t disperse its shots and give a beaten zone as is considered desirable in machine guns. Its bottom-feeding magazine limited capacity to 20 rounds, as longer magazines would have monopoded when fired from prone.
The BAR wasn’t great. We used it because we had it on hand along with tooling to produce more, but it was already outclassed before the war ever began.
This is a rather nice demonstration of the limitations of the BAR vs. the Bren by R. Lee Ermey.
Sort of an aside to the topic but interesting I thought.
Clyde Barrow liked the BAR.
One presumes he didn’t fire it as often as in WWII combat. 
Barrow used what was available. More advanced designs like the Bren or the improved versions of the BAR as produced in Belgium or Sweden (detachable barrels!!!) simply weren’t sitting in National Guard and police armories waiting to be stolen.
Ssssssorta. The .45 cartridge was invented in the 1870’s and later on was surplanted by a .38 caliber cartridge . But then the US got involved in the Phillipines and they found the .38 wasn’t enough, so they ‘brought back’ the .45.
Sledge didn’t use the famous Colt 45 pistol (properly called the model 1911), but a .45 revolver.
…and the 1870’s revolver and the 1911 use two different cartridges. The revolver used the .45 Colt, originally a black powder round. The 1911 uses the .45 acp,which was a smokeless round from the beginning. Some sources do claim that the .45 acp was designed to replicate .45 Colt ballistics as closely as possible from an automatic pistol.
maybe this guy sledge used a 1917 revolver chambered for the .45 auto.
That is a possibility as they were commercially available during the interwar years and were also still issued on a limited basis by the US military during the war.
I always thought it was “Automatic Cartridge Pistol” is it that or “Automatic Colt Pistol”.
Automatic Colt Pistol (for the 1911.) .45 Colt is for revolver and I think there are also lever rifles that fire it.
…I’m certain I can document as factual a fantastic confrontation that occurred in the waters off Guadalcanal between a Japanese officer with a sword and an allied officer armed with a .45 1911. A small allied ship (may have been a New Zealand ship, that I can’t recall) caught a Japanese submarine on the surface and rammed it. A Japanese officer, later confirmed to have been a Kendo (fencing) expert, tried to storm aboard the ship from the sub’s conning tower while the two vessels were in contact. Sword in hand, he was cut down at close range by an officer with a .45 1911. Famous true incident.
ACP is auto-centerfire-pistol. cartridges come in .25, .32, .38, and .45
I always wondered, given that my Fathers Beretta is .32 ACP.