Was thinking a 40K psi 10MM auto necked to 22 would be a cool round to work in a 10 auto but get 5.7 FN performance in a 1911

5.7 FN is a 50K psi round but the larger capacity could make up for the missing 10K psi in the 40K psi case.

60 grains @ 2500+ in a long barrel would be the goal with a simple barrel swap.

a short neck sharp shoulder design with about a .8" case length.

Think of it as a 357 Sig but smaller bullet.

Just a thought.

What are your thoughts?

Forming a shoulder and necking down to 22 caliber on a 10mm case will shorten the case considerably. You may want to consider starting with 10mm Magnum cases from Starline (10mm magnum is just a lengthened 10mm case) and trimming them to length after you form the neck and shoulder. You could also find that your pistol is very muzzle heavy with just a 22 caliber bore in the barrel. You almost certainly will have problems cycling the slide due to a lack of recoil with just a 60 grain bullet.
You may want to read this series of articles on a wildcat called the 17-357 RG about necking down a 357 SIG cartridge to 17 caliber.

Thanks so much!
Was interesting and informative!
Also maybe 6.8 SPC cases for the forming.
Was thinking that necking down that much might have some issues.
I like the 22 idea more though.

Here is the .17 version and what the 22 version would look like

Great minds think alike

.224 BOZ.

Thanks!
The 224 BOZ is pretty much what I was thinking but is about a tenth of an inch too long to work in a 10mm auto pistol unless you stick the bullets in far but I guess it could work. I'll do some more research on it.



Good to know I am not crazy =)

Alexander built Glocks and 1911s with six inch barrels in .224 BOZ. IIRC bolt thrust was a serious issue. Gas delayed blowback might be the solution.