Part of it is volumetric efficiency of certain cartriges.
Say, for example, you have a beautiful short rifle with a barrel length of 17 inches. It's cute, it swings quickly, comes to the shoulder and eye effortlessly and dagnabbit, it's just sexy. Let's say it's a Chilean Mauser- Cavalry model, 1895 in 7x57.
Now, suppose you have a second Chilean Mauser model of 1895, but this one is an infantry rifle with say, a 29 inch barrel. It's still relatively slim, but it handles like a shovel in tighter quarters, it doesn't come to bear as quickly as the shorter model, and it takes a couple of seconds or five to get a quick sight picture because you have to find that bobbling front sight almost a yard out there. It too is a 7x57.
Which one is more pleasant to shoot? The long-barrelled infantry rifle. The shorty is going to ring your bell with the concussion of burning gases still flaming out the end of the barrel. The longer barrel gives the medium-sized powder charge more room within the greater, but still enclosed space in which to fully combust. Your exterior ballistics are going to be better with the longer barrel, as time and distance are your friends, to a point. Otherwise, we'd all be shooting rifles with 10 foot long barels.
Now, to a more efficient carbine or pistol cartrige. My old 9mm AR shot pretty decent groups with the 16 inch barrel. 9mm is pretty efficient, volumetrically speaking, in a 5 to 7 inch barrel, but there was no need for a flash hider with the AR as everything was consumed within that 16 inches. It also goes without saying that I could make a lot tighter groups at 100 yards with it than I can my Browning Hi-Power.
Another example- the M1 Carbine fires a smallish .30 caliber round that doesn't have much recoil whatsoever. It was ok as a military round under most circumstances in close range social work. In my Ruger Blackhawk, however, it's a loud, scary flamethrower that will rupture eardrums 3 lanes down. 19 inches (or so) vs. 7 1/2 inches and a cylinder gap. Volumetric efficiency. It's losing pressure before the pressure pulse stars to drop due to the end of the combustion cycle in a shorter barrel vs. a longer one, although the mechanisms of the weapon design aren't factored in- gas op, closed breech vs. a revolver's cylinder gap.
Historically, carbines were issued to troops who would not normally be issued a long rifle but for whom a pistol or revolver was not satisfactory. Cavalry units and dragoons (although initially outfitted with a brace of pistols), engineers, artillerymen, cooks, clerks, drivers, and later, tankers were issued the carbine because they were not directly in an infantry role, per se.
Given a choice, I'd take an M1 carbine over a .38 Victory model if I were pressed into the front lines and a full sized infantry rifle was not immediately available. I bet I'd try to pick up the first longarm I could when I got there, though.
The late Col. Cooper was a proponent of a light repeating infantry carbine chambered in something along the lines of .44 magnum or .44 AutoMag. That probably would be a confidence-builder.
Regards,
Rabbit.
