An experiment even WB might like with the 40 S&W...

Have done similar experiments before & sometimes you get lucky with feeding but many times NOT! Will be interested to hear how you fare. Please also give us the stats on the bullets (manufacturer, weight, diameter, coating...) plus the terminal ballistics, thanks. Good luck!

Cartridge rim before entering the chamber fully. It’s much like the Mauser bolt gun. Because of this (the TC single shot rimless does this too) it can headspace off the extractor and supported enough to fire. It actually, the 10mm Glock, perfectly! Not that I recommend it.

I tried what you proposed in my AMT Javelina and it won’t feed at all with what I tried. The 1911 platform is finicky in comparison. Maybe with some bullet adjustments. On a dare once to prove it I loaded a .380 ACP in a Glock 17 9mm mag, chambered and fired it perfectly. It did not eject though. Again it was a unique exercise and not generally suggested.

I once made a chamber ring inserted into an Astra 400 in 9mm Largo. It stayed in the chamber allowing correct headspace. But that in no way addressed feeding.

albeit ever so slowly, to ALWAYS
wear glasses when doing such,
as well as ear protection and
soft leather gloves (they get
ever better with age!).

extract it. Nate and I were just talking about that. Kase was doing it probably 10 years ago. I think he also had a 10mm Longslide that would do the same. Nate nor I remember whether Kase had to fine tune the longslide extractor to make it work but it worked fine in both the Glock and 1911. And this was with factory 40 cal ammo, not working on the bullet at all.