Since the same revolvers handle both is there a reason 45acp load data can't be used in 45 auto rim?

Smaller internal case capacity?

In 1917, Colt released the M1917 revolver chambered in 45 ACP. As the 45 ACP was a rimless cartridge, the revolvers required the use of moon or half-moon clips to facilitate extraction and proper headspacing. These revolvers were issued to US troops in World War I to supplement the distribution of the M1911.

Although the half-moon clips were effective, they were easy to lose or misplace. If this were to happen, there are two potential issues. The first is failure to extract. Without a rim to hold onto, the extraction arm has nothing to grip and therefore rounds would have to be ejected from the cylinder one at a time with a field expedient object (think pencil). The second issue would be headspace. As the 45 ACP has no rim for headspace, it’s possible that a round could slip into the chamber and fail to fire.

To fix these issues, the Peters Cartridge Company developed the 45 Auto Rim in 1920. This new round was nothing more than a 45 ACP with a rim.

The new ammo allowed for the rounds to be fired and ejected without the use of a moon clip. 45 Auto Rim is compatible in revolvers chambered in 45 ACP, however it should not be used in a semi-automatic 45 ACP pistol.

I've used 45 ACP data in 45 AR cases. It works fine until you get to top-end loads. From there, you have to proceed on a gun-by-gun basis, just as you do every time you get to top-end loads.


Okie John

seems that commonly published data shows the acp is loaded to higher pressure. i'm wondering why.

Powder capacity is the same.

The NRA Handloading Guide says:

"The maximum average chamber pressure for the .45 Auto Rim is established at 16,900 c.u.p. This is less by 3,000 c.u.p. that the limit imposed on the .45 ACP, which should emphasize the advisability of loading conservatively for the old Model 1917 revolvers."

The #13 Speer Manual says the max is 15,000 c.u.p.

I use same data for both. Not plus +p by any means but middle of road loads

No.

okie john is correct.

The NRA Handloading Guide is telling you to load an Auto Rim (in so many words), to a lower level than the cartridge the 1917 WAS actually chambered for?
The real reason is that it (the 45AR) was factory loaded with lead bullets and they generally hit the same speeds as the 45 ACP did with less pressure. They also reduced barrel wear.

The 1917's might be old but they certainly aren't weak unless they've been neglected or damaged or not correctly repaired.

Another thing, 45 Auto headspace shoulders were cut into Colt 1917's, Smith 1917's, 1950 Targets, 25's, 26's up until the 1990's. The simultaneous ejection was the major hiccup in 45 ACP revolvers. Firing them was generally not, except in perhaps very early guns.

Until Starline started making Auto Rims, the case was generally prone to cracking because it was pretty thin towards the case mouth.

Complete guide to handloading by Sharpe, my copy 1937 makes absolutely no difference in loads for ACP or AR in the only powders still around, Unique & Bullseye. Amazing how the people including Hatcher were all wrong.

Were there any +p .45 ACP loads listed in 1937?

i understand, but weren't the moon clips designed to permit the acp to be used in those same revolvers?

The 1917 revolvers were a wartime expedient to use Colt's and S&W's current manufacturing capabilities to produce handguns quickly.

I assume the NRA publication's recommendation reflects 60 years of experience shooting full power ,45 ACP loads in these old revolvers? Just as some of Elmer Keith's 44 Special loads are now understood to be a bit much.

i get that but i'm not interested in elmer level loads, just the "standard" 45acp level loads especially in modern revolvers.

I would have zero concerns about shooting "standard" .45 ACP level loads, loaded in .45AR brass in a modern revolver.

They'll be fine. That's what they were made for.

Even plus P out of a perfectly fine working 1917 in good condition, especially the Colt 1917.

Heck, for that matter I would be comfy in shooting hotter loads in a Colt New Service than a copycat 1911 of dubious background. Those revolvers were hell for stout, within their genre, and I've seen some 1911 clones that would've been better off in the landfill. Back in my younger/impetuous days I hotrodded a few New Service revolvers (1920's vintage .45 Colt and .38-40, and a .45ACP 1917 to a lesser degree) with some hellacious loads and none of them whimpered. The .38-40 in particular got special treatment: 180 cast bullet + 8, sometimes 9 grains Unique, and sometimes I tiptoed over that line. Never a stuck case or any other signs of over-stress but I quickly backed off to 8gr. loads because frankly I was scaring myself. +P is ok, but +P+ in a vintage Colt is a sobering experience if one has a modicum of common sense.

Note however that Colt (and S&W) upped their metallurgy game in the 1920-1922 time period resulting in a much better safety margin over the WWI 1917 models. If I were to resume shooting a Colt 1917 I think I would hold up with standard pressure hardball loads as a maximum. As it is I'm quite happy anymore putzing around with mild semi-wadcutter loads in my Gold Cup, and occasional hardball sessions with another Colt 1911.

thank you all for your insights and expertise.
as i said, i'm not truing to use +p loads or emulate elmer kieth. i simply trying to understand that published 45 acp loads would be reasonable in the 45 auto rim. i still don't get why the auto rim wasn't loaded to the same level as the acp from early on.

It was

Julian Hatcher states in one of his books that the 45 acp and 45 AR were both loaded to 230 grain @ 835 fps for the military.

Phillip B. Sharpe states in his 1937 book once again that the factory load for the military in 45 ACP and 45 AR were identical 230 grain @ 835.

History of Colt Revolvers for the 1917 states that the AR round was identical to the 45 ACP except for the rim which was incorporated to get rid of the S&W half moon clips.

Good info here. I load the 255 gr Keith SWC to 45 ACP pressures in my 25-2.

https://www.handloadermagazine.com/45-auto-rim-p

Thanks for that link Ed. Brian must have done another write up on .45 auto rim which showed H Universal getting 900 fps with the 280 grain RCBS bullet. Unique is almost there with this data. I have not shot my 625 in awhile now. I remember that the fast 255 and 280 loads were stupid accurate though.

I have yet to shoot any game with those loads but the way they hit steel targets was impressive. very little blast or recoil.

I've experimented with 255 Keiths in .45ACP. While they do add impressiveness to the .45's performance I gave up on them, preferring the old 200 SWC instead. I reckon when casting all my pistol bullets by avoiding the super heavyweights I'm giving myself a free bullet with every five I make. Not to mention I don't walk around with a .45 for either hunting or self defense.

https://www.handloadermagazine.com/45-auto-rim-p[/quote]

the historical information is much appreciated as is the link

https://www.starlinebrass.com/45-auto-rim-brass

When Starline say "available for back order..." it usually ships in a few weeks. Great brass

I shoot mostly standard weight bullets but the heavy .45 Auto Rim loads turn the 625 into something next level for sure.

I have some 300gr. WFN loads for the 1917 Colt and 25-2's.

Powder space intrusion is LESS than the 452483, the 454424 and 230gr. ball.

Count me in on cast bullet masochism.

IIRC the RCBS SAA 270 was designed to put mass forward into the cylinder. Brian Pearce writing about it is the reason I own a 625 a .45 Colt Mountain Gun and a Ruger single action in .45 Colt.



I got to 900 fps in the 4" 625 1050 using 2400 from the Mountain Gun and stopped Way before I got into the "Ruger only" loads with the single action. Mine is the Bisley grip model and my hand does not like it.....

45 AutoRim and 45 AR Keith 452423 far right.

45 ACP and 300 WFN, third from right.

What is a 45 AR? Have you chronographed your 300 grain load?

It's an AutoRim bullet (AR). Lyman #452423; Elmer made a hollow point version too. Mine is cataloged by NOE and nominal weight is 240 grains. Its featured in 1955's Sixguns.

The 300 LBT clocks between 850 and 900 from a 25-2 with a decent charge of Longshot. That's as much as I've pushed it. It's also accurate due to overall bearing length and being seated and fitted into the throats.

It would do anything the 270 SAA will with slower powders like 2400, since it protrudes less in the case and provides more room for fuel (if one was inclined to do so).
It's sized .454 for the 25-2 and 1917 throats. A 625 would like a .452 bullet.

AA#7 would be another decent powder for next level 45 ACP/AR loads that still stay within modern pressure limits.

https://castboolits.gunloads.com/showthread.php?347916-MiHec-45-270-SAA-First-Year-Results

I ended up ordering a MiHec version of the SAA 270 that allows HP bullets of different sizes to be cast as well. This was the first results thread about this mold that came up. There is a longer one where probably a hundred different cast bullet forum members have raved about their results with this bullet.

Thanks again for more info about your efforts with the heavy bullets. I need to shoot something other than just paper and steel with this bullet.

https://castboolits.gunloads.com/sh...-or-45-AR&highlight=MiHec+45-270+SAA

More posts re heavy bullet loads

From Brian Pearce in Handloader #306-

There are no “weak” .45 ACP revolvers, as even vintage U.S. Model 1917 Colt and Smith & Wesson revolvers have proven completely adequate to handle these pressure levels, while all modern guns are rated for +P pressures.

I've loaded 255 gr. cast SWC's right up to 900 fps in my 1917.

Can you use .45 ACP dies for Auto Rim?

Yes

Yes, but you run into issues with crimping.

45 ACP dies apply a taper crimp and will apply a roll crimp if you screw them down far enough. Unfortunately, that applies a very strong taper crimp before it gets to the roll crimp, which crushes the driving band on the bullet and ruins accuracy.

To get a strong roll crimp without the taper, I had a buddy cut the bottom off of an extra 45 Colt crimping die. Groups shrank immediately. Someone probably makes a roll crimper for the 45 Auto Rim by now.


Okie John

My 45 ACP seating die (RCBS) applies a roll crimp if it's screwed down far enough. It does not apply a taper crimp. I had to buy a separate RCBS taper crimping die.

The die that taper crimps and roll crimps both, depending on the set, is a Profile crimp die.

Redding makes a 45 Auto Rim crimp die that allows a profile crimp which is an ambidextrous crimp; it will roll crimp in a cannelure or taper crimp a bullet without one.

It also allows a cast bullet with a crimp groove to still headspace off the case mouth if using ACP cases like the 300 grain bulleted load posted above.

The 45ACP, at inception, used a roll crimp. Tapered ACP crimp dies appeared after WWII.
The profile crimp die is pretty similar to how ACP dies were cut before the 1911 became a target platform.

I had a 1917 Colt and used the full moon clips. Lot cheaper than messing with auto rim cases. I still have a bunch of them and 2 of the removal tools.

You’ll only need a different shell holder.

I shot Hornady 230 gr +P factory loads out of my TC auto rim 13" barrel and got 1047 fps and I handloaded the same bullet in AR cases for 1028 fps. These loads were fine in my S&W 625 also.