Here's a question for the knowledgeable ones. As I understand it, the problem with rechambering or opening up an ACP to 45 colt is the gap between the recoil shield and the rear face of the cylinder. Thus 45colt rim thickness is insufficient to fill the gap usually filled by moon clips or Auto rim cases . Would it be possible to counterbore the cylinders to a shallower depth, in which the 45colt case would set back to the proper, I guess, head space? The loaded colt round depth could be controlled by the case mouth or the forward driving band as it comes to rest on the shoulder of the cylinder throat ? Would the unsupported portion of the rear of the case cause a problem ? Appreciate your thoughts SR

Why on earth would you want to do this? You gain nothing.

Wouldn't you gain considerable case capacity, heavier bullets without using all the case up yada yada yada...

That being said, that sounds like a dubious plan Riversalmon. I am not a gunsmith but head spacing a 45 colt on the case mouth sounds like a experiment I would avoid. Maybe just get a different cylinder that is a little longer. Or get a different gun.

JMHO

I have a 2nd MOdel Hand Ejector which was originally .455 Webley chambering, but, was later 'converted' to chamber either .45 ACP or .45 Colt.

Well, really, in such instances or in a re-chambered M1917, you can fire .45 Colt just fine as is, even if the Headspace is technically a little generous.

Just keep the Chambers clean so the Case can slide back and forth easily.


Or, what I did just for fun, I took a bunch of .45 Colt Cases, and, I deepened the annular 'ring' for them to fit into Moon Clips, thus giving me all the fun of the Full Moon Clips, a snug and tidy Head Space condition, and, even more fun than that, having them charged with .45 Colt Cartridges, instead of the usual .45 ACP.


If I can remember where I stored some images, I will post them.

The answers to your inquiries and others follows:

1. Not a good idea to rechamber a .45 ACP/auto rim cylinder to fit .45 Colt. The grossly excessive rim-to-recoil shield dimension will give erractic ignition.
2. The chamber internal throat can not be used to "headspace" a cartridge. It will result in greatly excessive chamber pressures, and very likely, a VERY impressive ka-BOOM cylinder failure.
3. It is possible to rechamber a .455 cylinder to accept both .45 Auto Rim and .45 Colt. It is a matter of carefully controlling rim diameter and counterbore depth while re-cutting the chambers. Tricky, but not impossible.

My suggestion is to leave the 1917 as it is. There are a bucket load on 45 colt's that S&W made. If money is tight, I would sell the 1917 and then look for the 45 Colt.

johntraveler, I'd like to learn some more about the "dual counterbore" to use both .45 Colt and .45 AR in a recut .455 cylinder. Seems to me that the counterbore for the larger of the two rims, .45AR, would have to be the deeper as well, removing any metal for the .45 Colt to stop on? Can you provide any details on the counterbore dimensions?

Larry

Hi John,
My intention is not be argumentative just clarify your meaning. As stated above Your #1 seems to contradict your #3. If you can shoot a 45 Auto Rim in the same chamber as 45 Colt, you have the exact same situation you warned about in your #1.

And your #2 describes exactly the way 45 ACP cartridges were designed to chamber in the 1917; they headspace on the chamber shoulder ("chamber internal throat" as you called it), not the rim.

__________________
Jim
S&WCA #819

Oops. I got my .45 cartridges mixed up.

It is possible to counterbore and chamber a .455 cylinder to accept .45 Colt and still accept and fire .455 cartridges.

It is NOT possible to counterbore and chamber both .45 AR and .45 Colt, since as you noted, the two rim diameters are too close in size and the .45 AR needs a deeper rim counterbore than the .45 Colt.

After examining drawings and dimensions, it should be possible to convert a .455 to take .45 ACP in moonclips and also .45 Colt rim counterbores. .455 capability is retained since it has a larger rim diameter than .45 Colt.

Not a contradiction at all.

1. applies to trying to rechamber a .45 ACP/.45 AR cylinder to accept .45 Colt. That leaves the .45 Colt head with greatly excessive case-to-recoil shield gap and unreliable ignition. The firing pin won't reliably fire the primer.

2. the warning against trying to "headspace" a .45 Colt cartridge crimp or bullet shoulder against the new internal chamber throat applies to cutting the tapered chamber throat required for .45 Colt. The .45 ACP chamber is designed to provide headspace on the MOUTH of the .45 ACP case. It is also not designed to butt up against the shoulder or crimp of the cartridge.

3. My mistake in confusing the rim dimension of .45 Colt and .45 AR. The reason a .45 Colt chamber can be cut in a .455 cylinder is that the .455 rim is thinner than for the .45 Colt which can be accomodated with a deeper counterbore. It is also larger in diameter which still allows .455 to be fired in the new .45 Colt chamber.

I once owned a 1917 S&W that had been converted to 45 Colt. It looked like a previous owner had started by pinning moon clips to the cylinder along the outside edge of the cylinder. The "fingers" of the moon clips that extended over the extractor were cut off and seemed to be soldered directly to the extractor. The pistol was then rechambered to 45 Colt.

The conversion actually worked pretty well, though I do not think I'd do one.

The attempt to use a chamber throat to get proper cartridge "headspace" would be a disaster.

To cut a shallow .45 Colt chamber to allow the cartridge crimp to jam up against the chamber throat sets up the stage for a ka-BOOM scenario where the ignited cartridge has no room for the case mouth to uncrimp and expand to release the bullet. Chamber pressures would be catastrophic and cylinder failure (especially in unheatreated pre-1930s cylinders would be almost guaranteed.

Yes, I am aware that the .45 ACP chamber uses the case mouth to headspace the cartridge. I also know that some competition shooters load their ammo to allow the bullet shoulder to butt up against the throat to minimize headspace variations and increase accuracy. That is an entirely different situation from intentionally using the tapered throat of the .45 Colt chamber to "headspace" a cartridge that does not properly fit the cylinder.

walnutred's description of pinning a cutdown moonclip to the .45 ACP cylinder describes what I have seen: intentional effort to lengthen the cylinder by soldering or epoxy gluing a shim to the back of the cylinder and then rechambering to .45 Colt. It looked like hell, but apparently worked.

Hi riversalmon,
You ask a very common yet valid question. You understand the situation perfectly and there is nothing wrong with your solution. Just to be clear, you propose reaming to extend the chamber, not counter boring. After all, the 45 ACP cartridge uses the exact same principle as designed at the factory, to wit; the case mouth headspaces on the chamber shoulder which allows the case head to extend a little out of the chamber exposing the cannelure (that cut groove) just above the rim. That's exactly what you're proposing for the 45 Colt and the small amount required is minimal.

The only caveat is that only solid head cases could be used. 45 ACP and Modern 45 Colt are all solid head cases. However just so you know, old 45 Colt cases were not solid and are referred to as balloon head. It's not likely you'll ever run into those these days, though they are easy to spot without even looking inside; they do not have the cannelure above the rim. If any case has a cannelure it's a solid head.

Normally you would want the entire case head supported up to the rim by the chamber, but as stated above, it's not an absolute. I would certainly not use any blockbuster loads in a chamber so modified but I'm quite sure you won't be using those in a 1917 anyway!!

Now, having said all that, I don't feel it's necessary to have the 45 Colt case stick out to reduce the rim-to-recoil shield spacing and you can prove it with your revolver before you spend any money on modifications. Take six 45 Colt cases and cut them short so they will chamber all the way to the rim in you revolver. If you reload, load them with a light load and shoot them. Except for wear or differences in manufacturing variances of your particular revolver, they will all fire reliably. I know this because several friends have their 45 ACP chambers reamed for 45 Colt and they work fine. If you don't reload pull the bullets and dump the powder from loaded 45 Colt rounds, shorten the cases and fire the primed cases only. Be aware the primers will set back out of the primer pockets and make it hard to turn the cylinder. That's not a problem.

Note: That's what happens EVERY TIME a round is fired. It's just that the primer alone does not have enough power to set the case back hard enough against the recoil shield to reset the primer in the pocket like a loaded round does. You can overcome this in your experiment by drilling the flash holes larger before you prime the cases (just as is required for shooting wax bullets for indoor practice).

If the 45 Colt rounds do not fire reliably in your revolver, I would not hesitate to ream the chambers slightly shorter as you propose. You'll need to taper crimp the 45 Colt so you have a case mouth to seat on the chamber shoulder. My measurements indicate they only need to be a maximum of .030" shorter, the difference in thickness between a 45 Colt rim and the rim of a 45 Auto Rim.

You'll gain an ability to shoot 3 cartridges from the same cylinder/revolver; 45 ACP, AR and 45 Colt.
Let us know what you decide to do and how you make out.

__________________
Jim
S&WCA #819

John,

45 Colt and 45 ACP chambers are the same size, .480" and once reamed longer the chambers would be a proper fit.

The 1917s were the 1st S&Ws to have heat treated cylinders and they all are. They were made under a government contract which required it. And all S&W cylinders were heat treated by c. 1920.

Of course the 45 Colt would have to be taper crimped (which I do anyway) to headspace on the chamber shoulder just like the 45 ACP.

Therefore I'm afraid your fears seem to be unfounded.

__________________
Jim
S&WCA #819

Jim,

I am still having difficulty accepting the proposal that deeping an existing .45 ACP cylinder chamber to accept .45 Colt is a good idea. The proposal was not for a longer cartridge that headspaces on the case mouth like the .45 ACP, but for the .45 Colt, which has a tapered chamber-to-throat leede. All standard .45 Colt chambering reamers have this taper built in. It is SAAMI standard.

Unless you are describing the use of a special .45 Colt reamer that cuts case-length chambers with a headspacing step, it is not a good idea. True, modern solid-head brass should hold up well to the mild .45 Colt ammo you want to fire in these converted guns.

My point being that it was not a good idea to fire .45 Colt cartridges in a chamber modified to use the tapered or crimped case mouth as a surface to establish proper headspace. The proof pressures for .45 ACP are only some 25-30% higher than service ammo pressure.

Remember all the M1917 S&W revolvers released by Government surplus back in the 1950s and 1960s? How often have you seen surplus M1917 cylinders and barrels for sale? Not often, I am sure, as I have searched diligently for them too. Barrels are commonly damaged from bore obstructions and corrosive primed ammo.

A major reason why surplus .45 ACP cylinders are not easily found is because they were mostly used up in refurbishing and repairing inventory M1917 revolvers. An awful LOT of M1917 revolvers must have needed cylinder replacement from bulged chambers, hard extraction, and corrosion damage. I am betting that many of these cylinders got damaged from firing service ammunition stored under adverse conditions.

Can or can you not load heavy bullet .45 ACP's to the same power level as .45 Colt that are safe to use in a 1917? With modern powder and cases I believe you can and if so then this conversion makes no sense whatever. I am talking about a conversion today not what was done in the past when 1917's were cheap and plentiful. Keep in mind that these guns may have heat treated cylinders but they were built 90+ years ago I would limit them to standard pressure ACP's or Cowboy .45 Colt loads so I ask again, not if it can be done but what do you gain?

and one I wouldn't take for granted cause this stuff is pretty subtle and I ain't a pro by a long shot. Hodgdon is pretty good about publishing pressures so I went to the hodgdon reloading data page and compared 45 colt to 45 acp. You can only go up to 230 because they don't list 250s with the ACP but even at 230 you can clearly see higher pressures consistently for equal or lower velocity with equal weight bullet. I would expect that trend to be even worse with heavier bullets which use up the case more. That is what you would expect intuitively. Surely there are plenty of exceptions waiting to bite my *****, but that seems to be the general trend.

Is a Model 1917 .45acp cylinder long enough for a .45 colt cartridge?

Yes...


If the question is that of whether converting an erstwhile Model 1917, .45 ACP S&W Revolver to chamber and fire .45 Colt Cartridges is justifiable, then, we would need to review the reasons which would justify it.

If the question is one of can it be done, and, how should it be done, without need of justification, then that is what would be reviewed.

Certainly it can be done and has been done, and, all one need to is to have the Cylinder Chambers Reemed by a competent Gunsmith to accept .45 Colt in a normal way, where-upon one then may confront the Head Space question.

With a generous Head Space this arrangement provides, the .45 Colt Cartridges should fire just fine and cause no troubles of any kind, so long as the Revolver has a standard power Main spring, and the Cylinder Bores and Cartridges are relatively clean.

.45 Colt is a regarded as a 'low pressure' Cartridge, and with the 'Solid Head' Cartridges which have been the de rigeur for a Century now, the little teeny bit which the Base sticks out of the erstwhile/converted .45 ACP Cylinder, is merely the end of completely solid section anyway, which extends up much further, so, no worries about the Cartridge somehow bulging or rupturing.

If one somehow is using ancient Balloon Head or Folded Head Cartridges from the mid to latter 1800s, one might get a little bulge or one might even get a rupture along some areas of the Case base which is sticking out...neither of which would be the end-of-the-world, especially if firing one Handed. If firing two Handed, the second Hand's Wrist might get injured a little bit.

Bystanders should never be permitted to be perpendicular to the Arm, anyway...but always behind...far as that goes.


Again, one very elegent 'Solution' to the Head Space question, would be to merely deepen the annular incised 'ring' at the Cartridge Base, and, to then use the ordinary .45 ACP full 'Moon Clips' for the .45 Colt Cartridge, which then establishes a Head Space in which the Cartridge is held 'back' toward the recoil plate thus ensureing no forward or backward movement to interfere with ignition or to invite annoying friction issues from post-detonation Primer protuberance.

In my opinion, I would have loved for Smith & Wesson to have offered their New Century and Second Model Hand Ejectors in .45 Colt, as well as offering them a great deal more in .44-40.


Oh well...they did not, and so here and there, now and then, there have always been boys and girls yearning or pineing for a Big Frame S&W DA which would accept the .45 Colt Cartridge, and, this is only natural!


S&W should have offered the 'conversions' for that matter! Might have helped them See the Light once all those Orders for it came pouring in!


Lol...

jimmyj,

Just to provide a little more detail even though you got the correct answer: yes the cylinder is long enough.
It's actually .030" + or - longer than a standard factory loaded 45 Colt with the traditional round nose flat point 250 gr. bullet, which is plenty.

If the cylinder was chambered as the original poster suggested to headspace on the case mouth instead of the rim would gain an additional .030" in extra chamber length for a total of .060" + or -; about 1/16" which is more than plenty.

__________________
Jim
S&WCA #819

riversalmon,

I think you probably got way more info than you expected. As usual in this topic of discussion you got the pros and cons on both sides of the issue.
To those that ask "why?" or "what do you gain?" I can only say if you have to ask, you'll never understand. Everything doesn't have to have a scientific reason for why it's done. In my opinion, "Because I want to or to see if it can be done." is as good a reason as any other. Most often that's my reason. "Some like black horses and some like Bays", and I respect anyone else's reason whether or not I agree but the conversation is always interesting.

I may not even ever try some of my ideas but the discussion is just as much fun with everyone bringing their thoughts and experience to the table as they have here in this thread.

I admit your solution to shoot 45 Colt in a 45 ACP cylinder is not only clever but a new one to me that I have not ever heard before, but I believe a sound and safe one none the less when you follow the logic as some here do and some do not agree with.

To sum up, if you go ahead your gunsmith will probably have some of his own ideas and opinions and will not do anything he deems unsafe. Some gunsmiths will do things and others will not as their opinions differ as well. If you use your idea, as John noted you'll want a square shoulder cut like the one in your cylinder now for the 45ACP, not a tapered shoulder as in cylinders that use cartridges that headspace on the case rim. And as I said you'll need to reload so you can taper crimp your 45 Colts. If you have the chambers reamed for a 45 Colt full length so they go all the way in to the rim, a tapered shoulder will sufiice and you can use off-the-shelf factory loads. That's assuming your gun will pass my test and fire shortened 45 Colt cases.

Let us know what you decide to do and if your pleased with it when completed.

__________________
Jim
S&WCA #819

I have seen a M1917 converted by using a .357 mag cyl that was rechambered into .45 Colt. That got around the rim issues, the .357 cyl will fit in the 1917 because it's similar in length, and you keep the .45 ACP cyl the way it is. It's a straightforward conversion, so it's not an exploration into the strengths of case heads, or the wisdom of headspacing, gluing spacers, or anything else. You just cut the cyl for .45 Colt and fit the cyl to the gun. Simple and does what you want.

That said, I don't think you can safely load the .45 Colt to high enough pressures to take advantage of the larger case in the 1917. Heck, you can't even load them hot for a modern M25. So you end up with a .45 ACP class cartridge with a rim. Since the .45AR pretty much does that, you can just use the money that the conversion would cost and buy .45AutoRim ammo.

You can do the conversion, but there isn't much you're going to gain from it. IMO not enough to justify the cost.

I suggest you get a spare .45 Colt cylinder and yoke, and have them fitted to the frame - then you can shoot .45ACP or .45 Colt with only a few seconds to change cylinders.

The main reason for not having a dual chamber setup has nothing to do with safety or conversion possibility. It has to do with accuracy, more specifically, the lack of it when firing short .45ACP in long chambers. There are a couple of forum threads about this, offering a lot of experimental results and as well as theory about why. The general thought is that a bullet fired from a short case will become unsupported in the long chamber, allowing it to yaw slightly before hitting the chamber throat. The resulting mass deformation gets accentuated in the forcing cone and rifling, the result being increased group sizes (2X or more), or keyholing if the bullet was not uniform to start with. This has been seen a lot in M25's in .45 Colt that have been cut for moon clips to allow both cartridges to be used.

Buck

Have thoroughly enjoyed the entire discussion and many fine points were made both fore and against. This forum is unique because when an idea strikes , here we have the knowledge and depth of experience to form, shape and eventually make a decision. It seems for the present, I will forgo a change to 45 colt. You fine gentlemen have however given me a lot to think on. Next, I will consult my ol' Amigo gunsmith, set the glasses up, and ponder the possibilities of maybe a *** palamino. Best Wishes Riversalmon

Look at the 1981 edition of Gun Digest.

There's an article explaining how to convert a S&W M1917 into .45 Colt. It's very detailed and would be an excellent read for anyone interested in this type of conversion. Even if you don't do it, it's worth reading. Heck the 1981 edition has quite a few excellent articles and it worth owning if you find one.

Anway, author C.E. Harris does just what you were contemplating, and I recommend reading it. Rereading it because of this post has refired my interest in it myself. Hondo44 has a great point in doing the conversion, just because.

Definately check the article out though. It's a wealth of information on this exact subject.

Thank You Ross for the suggestion and the source for some additional information. Now we'll see if I can dig up that book. Just by chance, did that Digest have an article on the Wondersight adjustable rear sight for older Smith revolvers? Thanks Again Riversalmon

Not to "HI-Jack" but I have a question:
In the late 1960s a friend purchased a disassembled Smith and Wesson .45 revolver that was not a Model 1917 but was "Supposed to be .45 Colt caliber. On assembling the revolver he found that a .45 Colt round would not go all the way in the chambers. He took a fine cut file and took a small amount of metal off the recoil shield. The revolver fired and worked fine. I have often wondered if this revolver might have been in .455 caliber??

Hi jimmyj,
I'm a little confused, why did he think it was "Supposed to be .45 Colt caliber" if the Colt round wouldn't chamber all the way?

Typically when a 455 gun was converted to 45 Colt the chambers were lengthened and the recoil shield was relieved slightly as you described to allow for the slightly thicker rim of the Colt cartridge. Sometimes instead of a slight amount removed from the recoil shield it was removed from the rear surface of the cylinder. When that's been done it is obvious because the serial number on the rear face of the cylinder is missing.

__________________
Jim
S&WCA #819

I'd have to look. It had a good write up on the .32-20, the handgun used in the article was a S&W Hand Ejector.