I had my 625-6 45LC Mountain Gun cylinder cut to accept 45ACP moonclips earlier this year. I only got to shoot a few boxes of ammo through it at the time but I was happy I did it.

I just got to take it out and shoot a lot more through it. I've heard people have had problems with accuracy shooting the 45ACP through 45LC cylinders (something about the 45ACP having more bullet jump through the longer LC cylinder) but I haven't noticed any appreciable decrease in accuracy.

I always wanted a 45ACP revolver and I was considering buying a 45ACP Mountain Gun, but overall, I'm happier that I can now shoot either. I wasn't going to cut the cylinder in my 25-5 in any case.

Anyone else tried this modification?

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Aaron Terry

always wanted to, never found the shop/OR the $$ to do such.

Got photos?
Where & how much, I may join your club!

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Dum vivimus Vivamas

<I always wanted a 45ACP revolver and I was considering buying a 45ACP Mountain Gun, but overall, I'm happier that I can now shoot either. I wasn't going to cut the cylinder in my 25-5 in any case.>

How is it still possible to shoot 45Colt in this gun that you have cut the cylinder to accept clipped 45ACP? Won't you have excessive headspace for the original 45Colt cartridge? I have a 625-6 MG in 45Colt. While clipped 45ACP or 45AR brass will chamber and extract, you cannot close the cylinder with that brass. How does one machine the cylinder to fit 45ACP or AR and still get the firing pin to light off a 45Colt???.........safely, if at all!

I haven't tried 45ar but I have a couple of 625's cut for moon clips and they work just Great, 1 I just purchased here a month ago shoot's just as tight as either of my 25-2's and 625JM 4".

I have 7 N frames 2-625 mg, 2-25-2's and 3-625's for 45acp and 2 of the mountain guns have been cut, and accuracy isn't compromised one bit,If your looking to get one done by all means got for it, its great to have a MG with dual roles.

On the parts section of this forum you'll find someone selling 2-625 fluted cly., thats a good start to have a separate cylinder for the project and have the best of both worlds.


There's several gunsmiths you can get this work done from, just check this forum and you'll find a few, I'm sure a few of the guys here will chime in with some gunsmiths in mind, Just my 2 cents worth.

Joe

Sir, as I understand it, such conversions are cut out only enough for a full-moon clip. That is, they're cut deeper on the inside (ratchet side) of the chambers to accommodate the clips and leave the cylinder full length at the outside. .45 Colts headspace on the remaining outside "lip," so to speak, while full-moon-clipped .45 ACPs are allowed to drop in deeper. The old WWI half-moon clips do not work in such conversions.

I've seen photos of such conversions that would help explain this better than I'm doing, but I can't find one right off. Perhaps someone else can post one.

Hope this helps, and Semper Fi.

Ron H.

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Wishin' don't make it so.

I had it done and I'm very happy with it, you have to have the cylinder cut were you have to use moon clips on both rounds to use the half clips.

The rim thickness left as an outter ring - to catch the .45 Colt's rim - will also catch the Auto Rim's thicker rim, preventing the cylinder from closing. That will be the same result as with an un-converted .45 Colt MG. Look at the moonclip conversion as only a means for shooting moonclipped .45 ACPs. Certainly, un moonclipped .45 ACPs will fit... but they won't be 'stopped' until they hit the deep .45 Colt cartridge case step. You'd have to borrow the long snout firing pin from an 1895 Nagant to reach the primers then!

I have two .45 Colt MG's, a -6 & a -7. I started reloading just for .45 Colts, over eight years ago. The ammo cost has always been high. I also have a 625JM for .45 ACP/AR. I won't be modifying my MG's.

Stainz

Thanks to Ron H and Stainz, I can now visualize this mod. Still seems kind of rinky dink, as the 45Colt case rim would only catch on a small part of the cylinder rim. Seems like a mod that will result in those clipped 45ACP rounds having to make a VERY LONG run to the cylinder throats, and the 45Colt rounds kind of "drooping" down in the chambers due to lack of proper support. I would be surprised if a gun so modified would deliver any decent accuracy.

That's what I thought at first, but I haven't had any issues. Has anyone had accuracy problems? The only negative to me is that you can't shoot 45ACP rounds without moonclips, but I wouldn't necessarily do that often in a 45ACP revolver as you'd have to push them out anyways.

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Aaron Terry

If this mod is such a good idea why hasn't the factory done it?

Because the factory would rather you buy two revolvers

Touche'...

At least 95% of all of corporate America is fully infected with NIH (Not Invented Here). If they didn't think of it, they ain't a'doin' it.

In addition, and even worse is the fact that virtually all of corporate America is run by people that have MBAs. The MBA program teaches them that you don't try to please all your customers, only the majority. That leaves a whole lot of us out in the cold, but they don't seem to notice.


Cat

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Think for yourself.

I had the same conversion done to the same gun: a 625-6 MG in 45LC. I have had no problems in shooting 45LC and no accuracy problems with .45 ACP. Glad I did it as I cannot find 45LC locally.

Am I correct in my assumption that this modification reduces the value of the gun if I am ever so dumb as to want to sell it? (I think that I have ultimately regretted selling any of my guns, with the exception of a Kahr 9mm that ..., well, never mind).

Here is a conversion done a while ago on a 625-6 mountain by Pinnacle.
I'm very pleased with the conversion
I would only do it on a newer piece like this with the tight .452 throats

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PC semiauto collector

Can somone explain the history behind the change in chamber throat size in 45ACP revolvers? I use to know this but I am fuzzy on it now...

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Aaron Terry

Jeffery,

No drop in value to me, I can tell you that.

Oh wait, yea, no, that's it, I'll give ya $300 for it, yea, that's it.

Thanks for the pics Grinder. Can you post one of two or three .45 Colt cartridges chambered too please?


Cat

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Think for yourself.

A bit of history on the .45 Colt cartridge and chamber.

It was introduced in the M1873 Colt Single Action Army revolver and adopted by the US Army.

Being a black powder cartridge, it was determined that chamber and throat tolerances would be on the "loose" side for reliability in sustained fire (combat) situations. 0.454" bullet, throat, and bore diameters were on the slightly generous side to allow for accumulation of firing residue and to allow for continued firing under conditions that did not allow immediate cleaning and lubrication. Chamber throats will routinely be found to be 0.456" and LARGER in both Colt and S&W products in .45 caliber. This was a routine production expedient during the black powder cartridge era (1870s thru WWI).

During WWI, S&W N frame revolvers were adapted from the previously chambered .45 Colt to .455 British caliber for British Army requirements. .45 Colt throat, bore, and groove diameters were used because they were very close to the .455 specifications.

When the US Government assumed control of S&W M1917 revolver production, it was determined that .45 ACP proof pressures were significantly higher than that of the previously chambered .455 cartridge. Because of the urgent need for M1917 service revolvers, the decision was made to make chamber throats to the previous .45 Colt and .455 British dimensions, namely 0.454"-0.456". This resulted in two things: increased combat reloading ease, and ability to pass the required .45 ACP proof test without the increased strength of heat treated cylinders.

In a nutshell, that is why S&W revolvers chambered in .45 ACP seemingly have oversized (.45 Colt sized) throat diameters.

If Grinder did it, it must be good idea.

How does it shoot with .45 ACP and .45 Colt? Can you tell the difference while firing, point of impact, recoil, etc.?

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N.R.A. BENEFACTOR Member

Back in the early '90s, I had it done to a 25-7, 2 625's, a Redhawk, an Anaconda and a 629 that we first rebored to .45 Colt. The idea came to me when I saw that a gunsmith was moonclipping 629s. This was before the factory was moonclipping N frames for rimmed cartridges. I asked the late Art Leckie, Austin Behlert's son-in-law, to do the milling. They all came out perfectly. Point of impact was always the same, given that the bullets were exiting with the same velocity.

The Concept is sound and has been done for years. That having been said, I would do the conversion on a new 625 and remove the lock. Leave the old hammer pin ones original for the next generation so they can see how a real revolver should look. I have two MGs, one in .45 LC and one in .45 Auto. They are staying original and being passed onto my nephew and his kids.

I had it done by Mark at Pinnacle also and love it, The gun shoots just as good as before and now I have 2 cals to pick from....my 625mg has never been happier.

John Traveller: I have a dim memory that at some point in the past you posted a comment that you found that you had some accuracy problems with this modification. With moonclipped .45 ACP? Or am I just misremembering? (I recall being concerned as I had just sent my 625 cylinder off to Mark at Pinnacle.)

john traveler--thanks for the info on the chamber sizes.

jeffrey--not sure about others, but I have not had any accuracy issues. The only negatives I can see to it are when compared to a standard 625 in 45ACP are that you can't fire the ACP rounds without moonclips and you have to use full moonclips, not the half or third ones (I have only heard about the latter, have not tried other moonclips). But I don't think I would ever need to fire ACP rounds without moonclips--also, you can get faulty primer strikes on the 625s if you choose not to use moonclips.

Also, I prefer the tapered barrel profile of the mountain gun to the full lug barrel of the regular 625, at least in 45ACP. I didn't think twice having my 625-6 cut for the modification--if it were a WWI gun or something I'm sure I'd feel differently. I see this as a definite improvement in any case.

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Aaron Terry

The previously mentioned accuracy problems were with three samples of older .45 Colt caliber S&W M25 revolvers. They gave excellent/very good accuracy using factory 255g RN factory lead ammunition, and after the conversion gave only mediocre .45 ACP accuracy using factory Federal Match 230 FMJ ammo. It was never determined whether the difference in accuracy was due to oversized chamber throats or the 1/2" "jump" of the shorter cartridge in the longer chamber. I can only state that I would not be interested in converting my .45 Colt revolvers.

Thanks for the clarification John.

I have a slight oddity here and wonder if, at some point, Colt manufactured some of their revolvers to shoot both .45 ACP in moon clips and .45 Colt without.

I have a Colt I bought advertised as a New Service shooting .45 Colt. It arrived looking like a Model 1917 with black plastic grips. It has a lanyard loop on the butt. Forward of the loop is marked "US ARMY MODEL 1917", while rearward of the loop is marked "No" with space behind that for more digits. The 5-1/2 inch barrel is marked "COLT DA 45" on the left side, and "UNITED STATES PROPERTY" on the bottom of the barrel. Prancing pony logo on the left sideplate. S/N 2763xx in the yoke cut-out on the frame.

It shoots .45 Colt ammunition just fine. One day at the range I notice that the gap between the rear face of the cylinder and the breech face of the frame looks kinda' too big for .45 Colt, and I drop in a moon-clip of Federal 230 gr. ball ammo. Cylinder closes and gun shoots those just fine, too!

The cylinder shows no sign of modification. The chambers' throats are cut with the step in the correct spot for the .45 Colt, with no reamer marks, and the rear face of the cylinder likewise shows nothing.

I have fired a couple of hundred rounds through the big Colt without any failures. The firing pin seems plenty long enough to shove the .45 Colt cartridges forward until the rims are seated and still dimple them with plenty of energy. The brass and spent primers look normal for both catridges.

I just don't know how this left the Colt factory. Like this, able to shoot both cartridges, or did someone subtly alter it later?

Buff, I once ran into a father and son at the range who allowed me to shoot a Colt new Service that the father's father had purhased in the 30s and carried in WWII. This gun would also accept .45 Colt and .45 ACP in half-moon clips. It shot great, btw.

Many of the 25-5s produced prior to the ABC1234 serial numbering had oversized throats and had a reputation for poor accuracy. Perhaps this had something to do with it.

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Aaron Terry

Here is a pic with the .45Colt rounds

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PC semiauto collector

I presume that the 0.040" of unsupported case on the .45 Colt does not cause any difficulties like bulging or splitting.

Buck

It shouldn't with any reasonable loading.

Most .45 Colt cartridges have a slight groove just ahead of the rim, so that area is pretty much unsupported anyway.

Thanks Grinder. Nice pic.


Cat

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Think for yourself.

Hey-I'm in the middle of having a 25-5 8 3/8 worked on by pinnacle high performance, who was recomended by a couple of folks on this forum. Mark-the sole owner and opperater at Pinnacle does a lot of this kind of work, and maintains that both of these rounds function well after his work. I am primarily interested in shooting ACP's out of a long barrel. I have used 255 gr lead SWC's in my 625-8 and my 25-2 with very favorable results. They are, after all, the same diameter-.452, and they seem to handle a fairly heavy charge very well. The gun is at Pinnacle now, and probably will be for a while because it is a one man show. I plan to post my results and some photos when I get it back and have shot it, because I really actually launched this project on this sight. You can email me if I can help at [email protected]. take care, flapjack

SW Governor shoots Colts and ACP with moon clips. Is the cylinder machined same?

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Tommy

Groo here
They have as all the PC 357mag guns cut for moon clips[fast reloads]
are cut the same way.

I had a 4" 25-5 that was cut for moon clips. It seemed to shoot everything I tried in it about the same (Colt & ACP in LRN, LSWC, FMJ and JHP). It had the over-sized throats so mine wasn't a tack driver but at app. 10 yards offhand, they all were acceptable SD groups.
I sold it to a buddy that wanted it worse than I did and he's tickled to death with it.

Necrothread - over 4 years old.

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NRA Benefactor Member

Didn't notice, interesting non the less.

Just don't be tempted to shoot .45 Winchester Magnum rounds through this type of conversion.

I have had the gun back from Pinnacle for some time now, and have arrived at what is the ideal solution for me. A member here suggested that I try 45 Winchester Magnum brass in the moon clips in my gun, loaded to the 45 Colt level. This brass is only an eighth on an inch shorter than the Colt brass, and resembles a very long 45 ACP. Works great-good power and accuracy, and with no more hung up brass when trying to eject the Colt cases from my 25-5. Flapjack.