Shooting 40 S&W in a 10mm Semi Auto?

[KCSO]

Works till a case slips out of the extractor, then it doesn't. You decide how much you and your gun is worth.

[scattershot]

Military Arms Channel on YouTube just released a video on this very subject. No problems. Long term usage may damage the extractor,though, IMO.

[reddog81]

I've shot small amounts of 40 S&W out of my Glock model 20 and my Delta Elite. It works. The flat nosed bullets used in .40 and 10 won't ignite a primer if a case somehow gets lodged in the chamber. A new Glock extractor costs under $20. I don't make a habit of doing it, but I wouldn't be too concerned about it if necessary.

[Lloyd Smale]

yup that's the real problem with doing it over the long haul. Ive done it in my 22 glock and it worked fine. But plan on using a wire brush on your chamber every time you do it and even then if your talking 10k rounds your going to probably end up with a rough chamber. As to extractor were or headspacing ill say this. Realisticaly all semi autos headspace on the extractor. If you loaded 10mm so that it actually head spaced on the rim it wouldn't take many rounds to gum the gun up and reduce reliability. Youd also have to trim brass regularly and I can honestly say I haven't trimmed handgun brass in 30 years. My guess is 99.9 percent of the ammo that goes through semi autos doesn't have the rim touching a thing.

One other issue that may come up is the same as 38 spl in 357 and 44 spl in 44 mag. you may develop a carbon fouling ring in the longer chamber causing problems when the longer case is used. Normally the extractor is there and the case mouth cushions the pins blow. In this the firing pin is going to be taking the hit on its face from the firing pins hit. Probably not a big thing but not the way it was meant to work.

[35remington]

Lloyd, I measured for just that, not guessed.

The extractor rarely headspaces the round. Very very rarely. It is not hard to determine.

The amazing thing is no one bothers to check whether it is occurring before giving their opinion. It is not that hard to do yet no one does it. If they had tried to see if it was occurring pretty much nobody would be saying it.

As a practical matter when a round is fired in a semi auto using the correct ammo in the correct chamber the extractor is not doing the headspacing in the vast majority of instances, which is the reverse of your declaration.

[Petrol & Powder]

Semi-auto, rimless cases do not "head space on the extractor" by design. Yes, the extractor may hold a casing that is shorter than the chamber against the breach face and allow that shorter casing to fire but that is not how that system is intended to work.

Rimless casings such as the 9mm Luger, 40 S&W, 45 ACP, etc. are designed to head space on the case mouth.

I think this falls into the category of things you can do but shouldn't.

[Elkins45]

Before I had my custom throated 40 barrel I tried seating bullets long in 40 cases and shooting them in a stock 10mm barrel. I seated the bullet out far enough that essentially it was headspacing by the bullet resting on the rifling leade. In the first 50 rounds I fired I experienced two very strange hangfire incidents where there was a noticeable delay between the hammer fall and the ignition of the round. It’s way too much of a coincidence to imagine those were bad primers so I figured the case was too far forward and the primer just barely got enough of a tap to set it off on a ‘slow burn’ ignition. The gun in question was my S&W 1006.

I immediately stopped shooting those rounds in that gun. No reason to take the chance with my fingers IMO.

[9.3X62AL]

I can understand people doing this in a "field expediency" or "emergency" scenario, but as a matter of common practice I have not and will not try it. I don't even shoot "Special" loads in "Magnum" revolver chambers anymore, because I dislike cleaning out the crud rings formed by this practice from the chambers. Well-fit brass is how I roll. The End.

[Lloyd Smale]

may not be a theroretical design but its a practical fact. Any time you trim a case so it doesn't bump the camber mouth you headspacing on your extractor. trim a 1/4 inch off a 45acp and youll find they still run just fine in most 1911s and the same can be said for glocks sigs ect. Load those same rounds I something like a ruger Blackhawk 45 acp that doesn't have an extractor and you will see constant misfires and light primer hits. Tell me? Do you measure your chamber dimentions and trim your brass to exactly fit that chamber and bump up against the throat ever so gently. With a taper crimp I doubt you even could and if you could youd have to trim your brass to an exact length after ever shooting. WHO does that? Then if you did your ammo you custom tayored for that exact gun might be to long for your other 45. If you trim your brass short enough to work in any gun and the extractor didn't hold it in place youd get light primer strikes in everything. Just like you would see in a revolver. Santa or God doesn't hold that cartridge in the proper spot to insure your gun goes bang your extractor does. Even many bottle neck rounds work that way. especially if your using small base dies or bumping the shoulder back. Difference there is the shoulder still stops the case from expanding any bigger then the chamber. But in them you do have the ability to actually headspace on a shoulder. Most don't do it even in them though. Only real exception might be a belted mag set up to head space on the belt. No matter how short you trim or how far you set the shoulder back its still going to head space on the belt not the extractor. that is the real world not a technical explanation of theory. If it didn't 40 ammo sure wouldn't run in my 20 and 29 and it does just fine.

Semi-auto, rimless cases do not "head space on the extractor" by design. Yes, the extractor may hold a casing that is shorter than the chamber against the breach face and allow that shorter casing to fire but that is not how that system is intended to work.

Rimless casings such as the 9mm Luger, 40 S&W, 45 ACP, etc. are designed to head space on the case mouth.

I think this falls into the category of things you can do but shouldn't.

[HATCH]

I have shot 40 cal out of my 1066 and 1006 (back when I had those pistols) and it functioned fine.
Keep in mind I only shot a mag worth out of each of them.

[Petrol & Powder]

I'm sorry Lloyd but we're going to disagree on this.

Rimless casing may headspace on the extractor if the casing is too short to headspace on the case mouth but they are not intended to function that way.

[fatelk]

Interesting; this explains why .380 will fire in a 9x18 Makarov. I once accidentally fired a magazine full of .380 through my CZ82 and only realized my mistake when picking up the bulged brass (though the complete lack of accuracy was a clue).

I wondered why they all fired so well, even though the brass is shorter and smaller all the way around.

[35remington]

Lloyd, it is a misstatement to imply that since a case can be ground down to extra shortness so it can headspace on the extractor that this is what occurs with unaltered cases as the default condition.

The extractor lets a case go forward of the breechface quite a ways before it stops its forward movement. It has to, as a considerable gap must be present for the case rim to get between breech and extractor hook in feeding. If a considerable gap was not present the gun would not feed reliably. This gap must be much wider than the case rim. This gap prevents extractor headspacing from occurring. It is a very rare event.

Actual measurement, not guessing, using cases as they come from the factory or as commonly reloaded, in factory chambers intended for that cartridge, shows that extractor headspacing is something that really does not at all occur with any frequency. It is at best an extremely rare event.

There is no good reason for factory manufacturers to make a case super short, nor for reloaders to do so.

The idea that extractor headspacing is the default condition when correct ammo is used in chambers intended for it can be demonstrated to be very false if those arguing the point simply take the time to do some measuring.

Most do not bother, which is how mistaken beliefs get perpetuated. By all means do not take my word for it. Discover what is actually happening yourself.

Please note the term case rim, which is at the back of the cartridge, is distinct from the term case mouth, which is at the front of the cartridge. In the majority of instances with factory ammo in factory chambers it is the case mouth which is the headspacing surface. The extractor and rim are not part of this equation.

[DougGuy]

I personally would not advise shooting 40 in a 10 except in two instances. First, test the 40 that you may have to use in a worst case scenario, this would be about plan D or so, but just to make sure it will defend you SHOULD the need arise and previous plans A through C fall through. Second instance, the need suddenly arrived and you grab the first magazine you see, and it happens to be 40, but it still works....

[Walks]

When I had a Glock 20, I had a Wolfe bbl in .40S&W. It functioned fine ever time. It never occured to me to try .40S&W ammo in a 10mm Gun. Neither did I try it in my poor Colt Delta Elite. That gun went down the road after only 200rds of NORMA factory 200gr ammo. Loose as a goose. But in the Beginning of the 10mm's life, shooting NORMA 200gr ammo was the only way to get brass for reloading.

Fortunately the Glock .40's came out. I've had a Model 23 ever since. Got a Wolf bbl when they 1st came out. Then a 9mm Conv bbl.

I just don't understand the reason for trying to shoot ammo in a semi-auto pistol not chambered for it.

But I guess it's the same reasoning that had me jumping off the 2nd story roof with a patio umbrella when I was 8yrs old.

As far as shooting/cleaning longer chambers fired with shorter rounds. If you dry brush the chambers immediately after you finish shooting that gun for the day. Works best for revolvers.

It's a bit more with Lever Guns. But just twisting a too big wet patch/patches in a slotted tip pulled tight at the front of the chamber from the muzzle. And twisted back & forth a dozen times. Then followed by a couple/three dry patches the same way, solves the problem of "chamber crud build up". Ya gotta do it at the end of each days shooting.

These cleaning procedures worked very well with other Revolvers too.

[9.3X62AL]

True that, Walks. That crud ring is just a pet annoyance of mine in wheelgun chambers. A First World problem, for sure.

[rockshooter]

One thing I noticed firing .40 in a Glock 20 is that the cases hit me in the face all the time. I suspect that comes from the mass of the slide being so much greater in the 20. Other than having to duck cases, firing 40 in a 10mm works just fine for me.
Loren

[Lloyd Smale]

I don't shoot 40s very often in my glocks but I have done enough testing to make sure it works. I guess my thoughts are (and I know its probably silly) that if **** and I needed too I could still feed my 10mms. My guess is 10mm ammo would be a pretty rare commodity. Now what makes it silly is I handload and have plenty of ammo but years down the line when im gone and my grandkids are still kicking they at least wouldn't have to throw the 10mm guns away. For the most part though if I want to shoot 40s I grab a 40 out of the safe. But in all reality its no different then guys shooting 38s out of there 357 (which I also don't do on a regular basis) . It sure isn't dangerous

[baileyboy]

Well you can always use 10 mm brass and load lighter....Same with a .357. You don't need full power loads when fooling around..

What he said. Next we'll have some fools shooting 308s in a 30-06 !

[fatelk]

What he said. Next we'll have some fools shooting 308s in a 30-06 !

Just for the sake of argument, it can be done.