Does overall cartridge length make the 38 super more reliable in a 1911 platform then a 9 mm? I believe the 38 super Cartridge is the same length as a 45, and I know the magazines in 9 Can be finnicky and problematic.
Does it make any actual difference or is it all the same?
well, since Browning designed it for the .38 auto first, then it was up-sized to .45 .. length & power curve / mass have a lot to do with reliability..
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I understand the Super was the original design but I would NOT say reliability is in the cartridge. (Some calibers aren't capable in anything)
quality in design and machining will have more to do with reliability than other factors.
This is just generalization but holds pretty solid.
Lots of 38 supers have spent time in the competition so, generally, I think you might find more refined platforms which might, in turn, lean towards more reliability.
I don't have any 38 super but I do have a 9mm 1911 that runs flawlessly though I can't say that i have 1000's and 1000's of round through it.
If the pistol is properly set up (feed ramp angle, extractor tension and finish, a quality magazine locked in at proper height, correct spring weights and with ammo that is in spec.) it will be reliable regardless of cailber.