I built a spare 1911 top end in .40 caliber. It would feed fine when slingshotting the slide, but would seldom fire three shots in a row without some kind of malf. I spent much time with magazines, brands of ammo, throating, mainsprings, and recoil springs, and never managed to get the thing to work right.
Glocks originally had a lot of barrel throat on their .40s, and reduced the amount of throat twice due to case head failures. My 1911 barrel had almost no throat, so after running out of parts-changing ideas I began adding throat to the barrel, even though it fed fine by hand. I immediately started seeing base bulges on ejected brass, and I was still within the latest "considered safe" support (by Glock standards) when I had a case failure that blew the grips into splinters and locked the gun up. After picking the splinters out of my hand, it took a couple of evenings of BFH, brass punch, and prybar to get the gun disassembled; fragments of brass jammed in the works didn't want to let anything move without "gentle persuasion."
At this point I realized I had almost enough money in the project to just buy a working gun in .40 caliber. Further realization was that I could just shoot the pile of .40 S&W I'd collected through a friend's gun, which is what I eventually did. The pile of .40 parts is in one of my "was probably a bad idea" boxes.
Someday I may address the project again; the annoying thing was that after months of working with it, I never found any reason for what it was doing. It might stovepipe, it might just stick the empty case back into the chamber, it might fail to pick up a cartridge when going into battery... then it might fire an entire magazine with no problem. It's hard to diagnose an intermittent problem, particularly when it doesn't manifest the same way every time. (assuming there was only one problem...)
