January 06, 2006

Guns > S&W Revolver Question (Paging Dr. Strangegun!)

So I've known for a long time that there were revolvers that fired rimless automatic pistol cartridges, such as 9 mm, .40 S&W, 10 mm, and .45 ACP. I used to think they were sort of oddball novelties, but I've seen so many glowing reports about the latter three that I'm seriously considering a .45 ACP revolver.

Anyhoo. I've got a hypothetical question about Smith &Wesson's L frame. It's just a shade bigger than S&W's medium K frame, and smaller than their N frame. Here's the way I think of it: the K frame holds six rounds of .357 Magnum, the L can hold seven rounds (e.g., in the 686+), and the N frame holds eight (in some S&W Performance Center versions of the 627).

The L frame can also hold five rounds of .44, as in the 296. That's 5 times .429 equals 2.145. And with the 686+ it's 7 times .357 equals 2.499. (And I know those figures are sorta sketchy, which is why I'm letting other people do the heavy lifting on this question.)

So, my question is, couldn't the L frame hold six rounds of .40 or 10 mm? That's 6 times .40 equals 2.4. It seems feasible, at least. I realize that any gun with six rounds is at a disadvantage because the bolt stop notch* will be aligned with the bottom cartridge and creates the weakest point in the system.

Any ideas? Someone put out the Dr. Strangegun Signal.

*The bolt stop is the mechanism that stops the cylinder from rotating so that the top chamber lines up with the barrel. The bolt stop moves into the bolt stop notch in the cylinder. In most (all?) revolvers, the cylinder is designed so that the notch will be at the 6 o'clock position when it engages the bolt stop. In revolvers with an even number of chambers, when the top chamber is aligned with the barrel there will be a chamber directly across from it at the 6 o'clock position of the cylinder. The metal between the bolt stop notch and the chamber is therefore the thinnest point in the cylinder wall. In revolvers with an odd number of chambers, the chambers are offset from the bolt stop notch, and are therefore slightly less compromised.

Posted by lesjones | TrackBack


I'm looking at my 681 (L frame .357) right now and it's chamber entrances measure ~.384" dia.. Checking my .40 S&W match ammo gage (basically a piece of steel with a minimum chamber reamed into it) it's dia. is ~.429. We can figure that a .40 S&W chamber will reduce the cylinder wall thickness by .0225" (half the difference). The smallest cylinder wall thickness I measure is 3~.085" so the new, .40 S&W cylinder's wall ends up ~.062" - pretty thin, that's .45 ACP territory. The cylinder bolt cut is not well measured with calipers but I measure a depth of .041" (It's probably slightly deeper). Subtract that from .062" leaves .021" minimum wall thickness, pretty thin. Now looking at the cylinder and looking at a .40 round next to it to see where it ends up I'd say that the thinnest area on the cylinder is where the brass case walls are still pretty thick. Sort of where, on the case, a Glock in .40 S&W is still unsupported.

Bottom line. I think an L frame in .40 S&W would work fine but I doubt S&W will make them. In 10mm my WAG is that it'd be unsafe.

Posted by: Marc at January 05, 2006

45 ACP? Get the G30 ;-)

Posted by: SayUncle at January 05, 2006

Marc: Wow! I thought .40 was pretty close to .40 inches in diameter. 'Course, I did totally forgot about the difference between bore size and chamber size for all of those calibers. Duh.

Uncle: the 30 is the total shizznit Glock-wise, but the S&W 625 really turns my crank more. I also need a 1911. This may be the year of the .45 for me.

Posted by: Les Jones at January 05, 2006

I think it already has... *hunts* no, ok, the 610 was an N-frame.

I think your pressures are going to be too much for the chamber width, IMHO. .40S&W's pretty hot all by itself, not to mention what 10mm can make.

Hunt around for frames that supported .38-40, that'll give you a good start. Talk to Tam too.

Posted by: drstrangegun at January 05, 2006

RE: the 620 vs the 66. Got both in 4 inch, use the 620 more because it just feels better. Both fit the same holster. Giving serious thought to Magnaporting the 620. RE: the 45 ACP revolver. S&W makes the 625 in a 5 inch, which seems about perfect; been thinking about one of those, too, as a SHTF gun. Advantages: 45 ACP is common, available in a plethora of loadings, use of moon clips provides reloads almost as fast as magazines. And ACP is just a fun cartridge to shoot.
Disadvantages: it's always got 6, a single stack starts with at least 8 and may reload with 8. Not having moon clips is worse than not having magazines; a 1911 can still fire as a single shot without a mag, the 625 is useless without moon clips.

Consider the 45 Colt, available in the 625 as well. No moon clips needed, still works with speedloaders. I've got a Mountain Gun in 45 Colt, and love it.
Disadvantage: doesn't have the variety of loads as ACP, and Billy Bob's Country Store will probably have something in 45ACP on the shelf, almost certainly won't have anything on Colt. My Dillon cures the problem, at least for me, and all the bullets available for ACP work in the newer Colts (452 bore).
Conclusion: I can probably find something in the way of ammo for my 620 anyplace, 38/357 are proven cartridges, as is the 45 ACP in the 625. And, it's probably easier for me to carry a pile of spare moon clips than to try and find suitable Colt ammo.

Now, the alloy 325 in 45 ACP, that looks like it would be interesting. So would a 7-shot Magnaported 5-inch 625-size gun in 10 MM, if you could find ammo for it (and S&W actually made it....)

Gun show this weekend, will probably come home poorer (money) but richer (gun).

Posted by: Homer at January 06, 2006

Smith has done a six-shot .40 Cal L-frame: The titanium-cylindered 646.

The reason titanium is used is that steel isn't elastic enough: the 6-shot .40 is pushing the limits of cylinder wall thinness in the L-frame.

I have one. Let me know ahead of time, and I'll bring it in and let you shoot it.

Posted by: Tam at January 06, 2006

"a 1911 can still fire as a single shot without a mag, the 625 is useless without moon clips."

No, since the cartridges in the 625 headspace on the case mouth, it'll fire fine without moons. You'll have to pluck the empties out with your fingers, however, since there's nothing for the extractor star to grab.

"So would a 7-shot Magnaported 5-inch 625-size gun in 10 MM"

Not enough room in the N-frame cylinder for seven rounds of 10mm; they did offer the 610, as Doc Strangegun pointed out, which was a 6-shooter.

I have one of those, too, and extend the same offer I made with the 646 above.

Posted by: Tam at January 06, 2006

Tam: Ah ha! So they did make one. Cool. I'd love to try yours. Thanks.

Homer: You nailedit. Since I don't reload the ACP is much more appealing to me. More loads available, and lots cheaper thanks to Winchester White Box and similar. The moonclips are also an advantage for gun games that involve a timer.

Posted by: Les Jones at January 06, 2006

There's also that Taurus 45 revolver that gets good reviews.

Posted by: SayUncle at January 06, 2006

Yeah, but it's a five-shooter, and Taurus QC has been unusually spotty of late.

Posted by: Tam at January 06, 2006

Tam - I didn't realize the 625 headspaced on the case mouth, so you're right - it works without moon clips. I've got several wheel guns in .45 Colt, and assumed the ACP cylinders were chambered to the same depth. Don't know why I thought that, since doing it that way would make no sense. My error. I came home from the gun show this morning with a new 5 inch 625. Much many nice. After hefting the 325 and 625 I went with the heavier one, and the 5 inch seemed to have better balance. BTW, thanks, Les, for starting this. Now it's off to the range.

Posted by: Homer at January 07, 2006

Homer: Cool. I've talked myself into buying a gun, but as far as I know this is the first time I've talked someone else into buying one. :-)

Posted by: Les Jones at January 07, 2006

Les: Well, it's because I'm easy. (But please don't start a discussion on anything expensive until my budget recovers...)

Didn't get to shoot the new 625 yesterday - when I got to the range the RSO on duty asked for a hand because it was a busy day (I'm an RSO, too) and by the time things quieted down it was too dark to shoot. Without fail I will shoot it next weekend, and if you're interested I'll send you a range report on it.

Posted by: Homer at January 08, 2006
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