.45 Hybrid (again)


Not to start a whole 'nuther round of discussion, but was wondering if anyone ever found a box to go along with the 45 COLT head stamp and rim dia. of the old Colt with the S&W length that might give reason for its exsistance?

Any new info would be helpful as time has come for me to give this one a name.



If you are saying the cartridge case has the dimensions of a .45 S&W Schofield case, then it is a .45 Colt Government cartridge. It was fairly common for the .45 Colt headstamp to be used on these.



Thanks, and Colt Government is probably what I’ll call it as that seems to be the popular title. The mystery to me remains what the purpose of the combination of small rim dia. and short case length was as the .45 S&W that was also being made at the time (I think?) would work in just about any .45 revolver I can think of as well as probably being more suited to the extractor of the M-1909 with its slightly larger rim diameter. I was just hoping that since the last marathon thread on the subject someone had found these with a box that would explain its intended application.



I’m still not convinced that there is anything special about these cartridges. A few years ago I rounded up a bunch of my 45 cartridges, both Colt and S&W, and made measurements. The only difference I could see in the REM-UMC 45 COLT was that the rim diameter was slightly smaller (.509") than older BP S&W cartridges (.515"). That’s only .006", hardly enough to be notable. It’s true that this brought the rim diameter more into line with the old BP 45 Colt cartridges (.506") but I also found many modern 45 COLT cases that had rim diameters that were larger (.510").

As Dave said, I don’t think the larger rim of the 45 S&W cartridges made them unsuitable for use in the Colt revolvers such as was implied in COTW. Quite a few 45 S&W cartridges were fired at the Battle of the Little Bighorn and they seemed to work just fine in the Colt revolvers. In fact, the Cavalry was later issued 45 S&W on a regular basis so that troopers armed with either revolver would have workable ammunition without having the supply problems associated with two cartridges. It was not long before the long cartridges were phased out as standard issue.

Maybe there is a real reason for the REM-UMC 45 COLT cartridges but I think it may have been more imagined than real. Or, it may be that someone noticed the difference in the rim diameters and jumped to the conclusion that there must be a reason for it. It’s always nice to come up with a reason for something, even when one isn’t called for.

Calling them 45 COLT GOVERNMENT is just fine with me. But I don’t think we should assume it means anything other than a name that Remington may have attached to it. After all, there are many other cartridges with the moniker “Government” attached to them and it’s mostly for sales purposes.

As Dave said, a box sure would help. Until then, color me skeptical.



Thanks for the input Ray.

Does anyone have a “proof” REM-UMC 45 S & W version of the same vintage as the one above? Also, I’m not great with nailing down dates and have this between 1911 and the beginning of WWII when I think they stopped using the black case ID for proof. Can anyone narrow that down?

One thought I had was that Colt seemed to like to have “Colt” on ammunition that were otherwise usually called Smith & Wesson. Make it with a flat nosed bullet and call it a Colt… But then why wouldn’t Remington just use a 45 COLT bunter with the larger rimmed S&W brass if it was just a name game? The mystery lives!




I have one of the REM-UMC 45 COLT proof cartridges. It is the same as the regular cartridge as far as I can tell (except for being stained black).

Dick Fraser’s list of REM-UMC cartridges shows that headstamp being used from 1912 to 1921. I think the black proof loads were used until the beginning of WW II (1942).

He calls it Colt Gov’t M1909, which is incorrect. I think he meant to say it could be used in the M1909 revolver. Or, maybe he knows something we don’t and the answer lies there, somewhere. The M1909 cartridge was made up until 1913 or so and the REM-UMC 45 COLT cartridge was made from 1912 until 1921. Hmmmmmm.



I seem to recall having, at one time, a .45 with the S&W length headstamped PETERS 45 C. GOVT…???..Maybe this will help a little to nail down the terminology used back in the day…


Peters was the only company I am aware of that used the ‘Colt Government’ headstamp, and I think used only that one headstamp; WRA Co and REM-UMC used both the 45 S&W and 45 COLT, and UMC used only 45 S&W.



Do you know if the rim diameters of the Peters, WRACo, UMC or the REM-UMC 45 S&W you mention run as small as the REM-UMC 45 COLT? (.507 on the example I showed.)




Guy can answer about his cartridges but I still have the measurements that I took several years ago. None were as small as the REM-UMC 45 COLT rim. Original GI cartridges ran .514 to .516. Later boxer primed GI ran as high as .521. The two UMC 45 S&W that I had measured .520 and .521.

Original 45 Colt GI cartridges ran .505 or less. UMC BP ran .506 to .508, while later smokless loads ran .507 to .510.

Just for reference, the M1909 rim measured .535 to .540.

I consider all these differences as minor, well within normal tolerances. You can find similar differences between brands of modern cartridges made today.

All of the cartridges would work in an M1909 revolver so I can’t imagine a reason to make another cartridge except to cash in on the “Government” label. I totally disagree with the implications in COTW - that it was done for a military purpose.




It would appear the military considered the ‘large’ rim of the original externally primed .45 S&W cartridge to be problematic, as they reduced the rim from .525 to .513 on June 6, 1887 to prevent the possibility of overlapping rims when the cartridges were chambered in the (Colt) cylinder, this according to HWS Vol 1.
Measurement of the rims on my assortment of 45 S&W length cartridges revealed the following:

REM-UMC 45 S&W - .518" - .521"
REM-UMC 45 COLT - .507" - .510"
WRACo 45 S&W - .510"-.512"
WRACo 45 COLT - .505" - .507"
UMC 45 S&W - .519 - .521"
PETERS 45 C GOVT - .513"
early unheadstamped commercial example - .522"

I believe these measurements support Ray’s contention that there is nothing special about any of them. The 45 S&W headstamped cartridges have larger rims than the 45 COLT headstamped cartridges; those with the 45 COLT headstamp most likely were the standard REM-UMC and WRACo 45 COLT case shortened to 45 S&W length. I would have measured a number of Colt length 45 COLT headstamped cartridges by REM-UMC and WRACo to test this, but I was getting eaten up by mosquitos in my workshop and had to give up.


Guy and Ray,

Thanks so much for the dimensional info and sorry about subjecting you to the mosquitos Guy! We’re heading towards bug season up here but have a little time before the black flies make outside life miserable…

I agree these figures support that, while there is a measurable difference in general between those called 45 S&W and the 45 COLT short case, probably only extremes in chamber/extractor dimensions would cause any concern for a user.

Thanks again for helping me out on this one and allowing me to tap into your vast experiences and collections for info.

Best Regards,


Further to the rim dimensions Guy provided on April 2 I used an 1899 Colt single action cylinder in .45 caliber, a couple of loaded cartridges, and a feeler gage to discover that that cylinder will not permit the loading of adjacent chambers with cartridges having a rim diameter greater than .520 in. The Colt was originally produced in .44 S&W American caliber for Army tests and I suspect the cylinder diameter and distance between chamber centers remained fixed so that the .45 cartridge was a darned tight fit. The Schofield, coming later, had maybe a slightly larger cylinder? JG



The S&W revolver followed the Colt by only 2 years (1875 vs 1873). I don’t have a S&W revolver so can’t say if the cylinder was bigger or not. The original copper cased S&W cartridges had a rim diameter of .515 but I think the primary reason for the bigger rim was to ensure ejection. They worked fine in the Colt which used a rod ejector that was not critical as to rim size.

When the S&W cartridge went to the boxer primed cases the rim was increased to as much as .525" which apparantly caused difficulties in some of the Colt revolvers. So, as Guy said, the rim was reduced to .513" in 1887. That .513 dimension was evidently not strictly adhered to since the cartridges that I have actually measure about .520 to .521.

Much would depend on how “tight” a Colt cylinder was chambered. I would suspect that most martial revolvers were chambered on the large end of the specs to ensure their operation under most adverse conditions. Those revolvers would easily take a cartridge with an oversize rim although trying to chamber six such rounds could be a problem, which led to the official reduction in rim size.




Ray: It’s true the S&W postdates the Colt by only a couple of years, but, unlike the Colt, it postdates the cartridge too. The original SAA were in .44 S&W American. The dimension of .520 rim recess was based on a single cylinder, but I made up my mind in providing these figures I wasn’t going to do a general survey of any sort. Still, I’d be interested in hearing what the diameter of the Schofield cylinder is. Best, JG



I completely missed the point of your first post. Now I understand what you were getting at. It takes my brain a while to get into gear.

I’m wondering if the Colt cylinder diameter was actually based on the older 44 percussion revolver frame rather than on the 44 S&W American cartridge?

It would be interesting to learn the diameter of the S&W cylinder. But it could actually be smaller than the Colt. The distance between the bore center line and the cylinder center line would be the critical distance.