My common sense tells me this is probably a really dumb question. I receently acquireda
M-625-10. My curiosity overwhelmed me and I wondered if the .45GAP could be safely fired in a .45acp revolver. The rear ends would go into the moon clips ok, but would the GAP rounds famous pressure weirdeness overcome the strength of S&W's modern metallurgy? Regards; Al

The problem is headspacing. The 45 ACP and the 45 GAP both headspace on the mouth of the case. Because of the difference in length there's a good chance the GAP will simply be driven into the acp chamber by the firing pin blow.

Frankly I wouldn't do the test your comtemplating. Stick with the ammo designed for your gun.

By using the moon clips the Gap should fire and function just fine, accuracy may not be up to par, only shooting them will answer thae accuracy question...

Give it a try, and write back to let us know whether it blows up the cylinder...

>The problem is headspacing. The 45 ACP and the 45 GAP both headspace on the >mouth of the case.

That's what the clips are for. Early Colt Model 1917s were bored straight thru, and relied completely on the clips for headspace.

I've got a feeling that a modern S&W would hold up just fine to the pressure. My question -- why bother? .45 ACP is easier and cheaper to get.

Yup, I sure messed that one up. Revolvers, Revolvers, I have to say that ten times. I'm thinking auto's. I still probably wouldn't shoot the gap in it, but that's just me. After running a gunsmith shop for a number of years I've seen to many blown guns I guess.

Actually, the GAP round might work in a 1911, too -- although I would certainly counsel anyone not to try it. While the 1911 theoretically headspaces on the case mouth, in fact many of them "headspace" on the extractor, which holds the case back against the breechface. Again, a fool thing to try, so don't try it, but it might work.

I appreciate the responses. I hate to admit I am not adventuresome, but I don't like the idea of even trying that...It was just one of those nagging questions which get in one's head and won't stop. The biggest reason I have for not doing it is that the GAP round has a history of overpressure incidents. There's no doubt that the round would fit. Thanks to all who answered.

There is not a problem with pressure in the revolver that you mentioned..

I have a S&W 610 in 10mm. It is very accurate with 10mm stuff. It will also shoot .40 S&W with clips. I tried it, but while the .40 S&W worked fine, it wasn't very accurate.

I have a S&W 610 in 10mm. It is very accurate with 10mm stuff. It will also shoot .40 S&W with clips. I tried it, but while the .40 S&W worked fine, it wasn't very accurate.

Yeah, but that's an apples vs oranges thing.

.40 S&W isn't a shorter cartridge that produces the same ballistics as the 10mm. The .45 GAP is just that to a .45 ACP.

I'd say don't do it. To achieve the same ballistics with a shorter case, they had to have upped the pressure considerably. Your .45 ACP revolver is designed to handle .45 ACP pressures, not .45 GAP pressures.

While I may be wrong, and it'll work fine, I wouldn't risk my gun (or my fingers, or my eyes) finding out.

The Gap pressure is about the same as a +P 45 ACP should not be a concern in a revolver, That is the same as the 45 Colt Smith in terms of Cylinder strength and that means 25,000 PSI is doable...

It's an interesting queston. I've pointed out before that seating a .45 ACP bullet just 1/8" deeper in its case will cause pressure to go from a sedate 16,000-something PSI civilian level load (which seem to average about 350 ft-lbs for standard pressure, rather than the 390 ft-lbs or so the military loads them to) and drives it up to about 23,000 PSI, or +P+ level. This assumes the ancient 5.0 grains of Bullseye recipe under 230 grain hardball.

If you try the same stunt with the .45 Glock Automatic Pistol round with the same 5.0 grains of Bullseye, the pressure leaps from around 21,000 PSI to about 52,000 PSI. This is because the percent of the volume available for propellant gases to expand in is made so much smaller, percentage-wise, when you shove the bullet base 1/8" deeper into the GAP case. Since auto-loaders tend to push bullets in by recoiling the front of the magazine housing back against them and by shoving them rapidly up a feed ramp, this may explain the GAP pressure variation stories? I can only speculate the same problem would have arisen if the old .455 Webley round had ever been used for a semi-auto?

The revolver is another matter, as it tends to recoil bullets out rather than in, by pulling the back of the case off the bullet, whose inertia wants to keep it in place. Kind of like "pantsing" the bullet. Nonetheless, the N-frame Smiths designed for .45 ACP have pretty thin cylinder walls. The .44 Special in that same frame gets an extra hundredth of an inch of steel, which may not seem like a lot, but which counts for a surprising amount if you are Elmer Keith working up to magnum pressures. Chances are this would work, but I am with the others in thinking, why subject the gun to unnecessary pressure?

Nick; That is what I was searching for. A well-reasoned and explained answer. I appreciate the time you took. I firmly decided that I wouldn't try to substitute the GAP for an ACP, but curiosity drove to me seek an anwers to the question. Regards, Al