Firing a .22 in a .22 Mag chamber isn't too bright, either.
It is NOT like shooting a .38 in a .357; the chamber diameters are different. The result is a split .22 case, hot gases going where they were not designed to (with all the consequences thereof, rapid leading of the chamber if the practice continues, and a slow bullet coming out the muzzle.
I have seen a guy fire 40 S&W cartridges through a 10mm barrel. Seems like the extractor would hold the base of the case close enough to the breachface that the firing pin could get to it. The bullet must have made a "leap of faith" from the case mouth to the bore.
Hey, I've seen guys shooting 9mm through a 40 cal. pistol so I'm pretty sure it would fire in the pistol. I would imagine the edge of the chamber would be scraping jacketing from the bullet and getting a buildup of copper there pretty quick too. Would not be doing it unless there was no other alternative.
Here we go again. In a S&W M610 that uses half moon clips, yes. In a chamber that head spaces on the case mouth, no. The 40 S&W is .003 smaller in diameter and will slip forward or is driven forward in the chamber when hit by the firing pin. This leaves the cartridge base unsupported. The primer can setback, leak or even blow out allowing high pressure gas to escape rearward. Not a good thing. Bob http://www.thegunzone.com/10x40.html
I misquoted the article I read. The 40 S&W is .03 mm narrower in the web area, not in case width. The widths only differ by .001. The shorter 40 S&W case will try to headspace on the case mouth and can still be fired in the S&W M1076 that was the test bed. Maybe other autos too. Bob
With the .40SW case being .142" shorter than a 10mm case, and headspacing on the case mouth it will be too short for a firing pin strike in a 10mm chambered barrel.
The only hope is that it headspaces by the extractor hook.
It would fire in the S&W M1076. Quite nasty. The cartridge may not go all the way forward or may come out from under the extractor, I don`t know. The article I read is at the bottom of the page of the link I posted. Bob
In a S&W 610 revolver using half moon clips, yes. In an auto that head spaces on the case mouth, no. In a S&W 1076 auto according to what I read the firing pin has enough travel to fire them but the primers perforate or blow out causing hot gasses to escape toward your face. Bob