Everything I have read seems to indicate that .45 auto rim and .45 ACP loads are practically the same. However, my experience with my 625-2 is that the exact same load in an auto rim case has signs of higher pressure than when I load it in an ACP case.

I noticed it in two of my more common loads which are: 4.73 grs of 231 behind a 200 gr Hornady LSWC and 3.7 grs of Bullseye behind a Berry's plated 200 gr RNFP or SWC. All three bullets are 0.452" dia. Both loads behind all 3 bullets function perfectly out of ACP cases, but cause the case belly to expand in my auto rim cases which makes ejection somewhat difficult. All 3 bullets also seem more accurate out of my auto rim cases. I keep my revolver clean and had my chambers polished, so I know it is not caused by residue in the chambers.

My old Speer manual did have slightly lower ranges for auto rim versus ACP cartridges, but they were both pretty close. I was thinking that the pressure may be greater with auto rim because the rim forms a better seal for gases trying to escape out of the back of the cylinder. I have tried using a slight taper crimp rather than a slight roll crimp. The taper crimp seemed to have slightly less recoil and and reduced the amount of case expansion, but the case ejection was still a little sticky.

I was wondering whether anyone else who reloads .45 auto rim has the same experience?

In my experience they are exactly the same. The only difference is the rim.

Unless you are using bullets with a cannelure or crimp groove, you should be using only a light taper crimp...no roll crimp.

Trying to ascertain differences by recoil "feel", etc. is problematic. the only sure way is with a chronograph.

One advantage of the AR is the ability to use a roll crimp in bullets that can accommodate it. For example you can use a heavier bullet and load in an AR case than an ACP case because you do have the roll crimp ability, if you have the right bullet. A good choice for the AR might be the .45 Colt 255 gr. SWC hard cast from Missouri Bullet, also available in coated. It has the crimp groove. See:

Missouri Bullet Company

__________________
USAF, 69-92
Vietnam, 72-73

I'd be careful before assuming you can use a roll crimp in a 45ACP revolver.
The case still headspaces on the case mouth. The rim allows extraction without moon clips. That's ALL the rim does.

Not true! The .45 Auto Rim cartridge headspaces on the rim, which is why the rim is so thick compared to the rim on other rimmed revolver cartridges. If you doubt this, check SAAMI specs online for the Auto Rim compared to the ACP cartridge.

In my experience, if you check an Auto Rim[AR] case and an ACP case for water volume you will find the AR case has less case capacity. Either way, unless you are loading max. loads there will be little difference in performance.
The ACP or AR can both be loaded to equal, or better than a .45 Colt in modern guns.
If the subject really intrigues you ,try to find a copy of the article " The Best .45 Autos are Sixguns" by Skeeter Skelton, in the June 1973 issue of "Shooting Times" magazine.
For "hot rodding" the ACP you will be amazed at what can be done in the S&W 1955 Target and later versions, or if you're after ICBM ballistics try the Ruger .45 Blackhawk convertibles. You could nearly sell off your .44 Mags.! Best of luck in your pursuit. Nick

I use the exact same data for either...no difference in performance for me.

Randy

PS. The 45 AR doesn't feed very well in my 1911 though......LOL!

For what its worth, Hatcher, in his 'Textbook of Pistols and Revolvers'
lists the following data(from 1927) as factory data
45ACP 230 Gr Bullet 810fps
45ACP 200 Gr Bullet 910fps
45AR 230 Gr Bullet 810fps
45AR 255 Gr Bullet 740fps (Peters Cart. Co.)
the later matched the .45 Model of 1909's 255 Gr Bullet 738fps

So historically, from a ballistic standpoint 45ACP = 45AR. From a case dimension point, the cases capacity and dimensions are not the same:
45ACP case dia. @ mouth: 0.471"
45ACP case dia. @ head: 0.471"
45AR case dia. @ mouth: 0.472"
45AR case dia. @ web, rear: 0.475"
45ACP case dia. @ head: 0.512"
I suspect that the extra 4 mils in case dia. at the web is the source of DMY's observations about harder extraction with the AR case

Respectfully disagree. They headspace on the moonclip for ACPs or the rim for ARs.

In fact many of the more recently produced 325/625 chambers either don't have the "shelf" that permits headspacing on the case mouth for ACPs without moon clips or the shelves are cut too deep to be of any use. S&W chooses to ignore this, knowing that the ACP cartridges will headspace just fine on the moon clips.

__________________
USAF, 69-92
Vietnam, 72-73

I've loaded identical loads in my M625/4" & they are almost the same as my 1911/Comm. I then double checked with 45acp loads in the same gun, no real diff. Any pressure signs you are seeing is brass specific. Measure the internal volume of your 45AR cases, see if they are significantly less.
What you are likely seeing is the 45AR brass is thinner in the head area & you are getting some case expansion there. I've loaded some pretty stiff loads using 250gr LSWHP, 850fps. In acp or Ar brass, case head exp is minimal.

__________________
NRA Cert. Inst. IDPA CSO

Not really. Once you go to a moon clip, the headspace is off the false rim of the clip. Most 45acp brass wont even come close to headspace on the mouth in a M625.

__________________
NRA Cert. Inst. IDPA CSO

dmy you're not seeing signs of excessive pressure with your loads
which are basically at starting level. Isn't this the second time you
have brought up this issue of swollen AR brass in the middle of the
case? If you're actually seeing this it isn't because of high pressure.

I've not checked other brands but using new Starline brass, I've measured a capacity of 27.3grs/H²O for their 45ACP brass & 27.4grs/H²O for their 45AR brass.

Their 45AR brass is equally as strong as their 45 Super brass, which holds 26.8grs/H²O.

.

__________________
Waiting for the break of day

Dmy
I would just like to note the Hornady 200 gr. Swc is a soft swaged bullet, not a cast bullet. Load data is different for swaged than cast.
I also notice the starting charge for the Hornady is 5.4 grains of Win231 at 800 fps as shown in the Hornady handbook.

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I'd like to agree with you BUT

Same load in AR brass for my 625s and ACP brass for my 1911s.
200 LSWC over 4.2 grains of N310.
Works equally well in both platforms.
And the 255 grain pin smashers for the AR are a hoot, too.

__________________
-jwk-
US Army '72-'95

Groo here
The thing about AR brass is that it is not constant between
makers.
Starline [ best] can handle 45super + pressures but Rem
is very soft and will show pressure much faster.
Is your brass Rem?
If so get some Starline, keep the Rem for very light target loads.

"not constant between
makers."

That's true of any caliber. Not only that, but the same maker's brass will vary from lot to lot and over time.

__________________
USAF, 69-92
Vietnam, 72-73

I started out using Remington 45 Auto Rim brass since they were the only game in town at the time. Later on Starline produced 45 AR occasionally but I have never used it. Never had any problem with Rem. AR brass. If your AR brass is showing swelling near the rim, my question would be "are your cylinder chambers chamfered?".

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Bob.
SWCA 1821

Excellent point!!

__________________
USAF, 69-92
Vietnam, 72-73

If you are getting swelling of the brass at the base where a chamber is chamfered, that is at the thickest part of the brass in the web, and that would be an indication you have reached "beyond" the loading limit.

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H Richard
SWCA1967 SWHF244

Very good and valuable info. Yes, this is the second time I have written about swollen auto rim cases. I only have Remington AR brass because that was the only thing available at the time. I presumed that Remington would be decent quality. Most of the swelling is near the rim, but my chambers are not chamfered. I will have to buy some Starling and see if I have the same problem. Again, thanks everyone.

Are you sure that you're not confusing the normal ring left near the
case head by the sizing die with swelling? Your loads are low
pressure. I'll bet that a few good pics of the cases you are concerned
about will quickly lead to the answer.

Alwslate:
I am aware of the ring around the base of various cases, including my .45 auto rim cases, caused by the sizing die not resizing 100% of the case length. I presume this lower portion of the case is not causing the problem or at least it is not related to the lack of 100% resizing because I always put the first few finished cartridges through the plunk test using the actual revolver. In essence, I put each auto rim cartridge through the plunk test when I load it at the range. They all fall into the chambers like a hot knife through butter. When ejecting the empty case, some of the loads (as in all 50 cartridges previously loaded with that same bullet, powder, and charge) are sticky to difficult to eject. All of my auto rim cases were purchased at the same time and bear the same original lot number. I have never had the same problem with .45 acp cases, even when using factory 230 FMJ loads which are, by far, the hottest load I have put through my 625. Again, thanks for your response which is good knowledge.

Ok the only thing I can say is a few good pics illustrating your problem
would most likely quickly lead to some advice. The old saying "one
picture is worth a thousand words" still rings true.

Thanks Alslate. I will try my first attempt at posting photos the next time I have this problem. Currently, all of my auto rim cases are either loaded or already sized, deprimed and cleaned.

I have encountered that claim before, but do not understand how it can be true. Given similar pressure limits and bullet weights, the 45 Colt will always out-power the 45 ACP. That is like claiming the 308 Winchester will out-power the 30-06.

I don't think so.

I had no luck trying to find the Skeeter Skelton Article on line.

A long time ago I read a very serious debate concerning the differences between rimmed and rimless cartridges, pressure and tolerances. Those debating were of the vintage of Phil Sharp, Harvey Donaldson and Howe, I am not sure about the names of those in the discussion. Some favored the rimmed cartridge over the rimless and naturally there was the other side. The discussion got very technical and was very interesting to me. I have searched through my old books and cannot find the article.

I would appreciate it if anyone can come up with a reference.

One thing I have noticed is that my the rims of my Starline AR brass swell over time and after about 40 reloadings will not fit in my shell holder. Once I accidentally loaded way too much powder in one cartridge and recoil was strong, the bullet hit about 7 inches low at 50 yards, but the case did not stick and with a micrometer I could not find any differences between it and the other spent cartridges, nor could I see any difference in the primers that would indicate high pressure.

Any thoughts will be appreciated.

I use both Rem and Starline AR cases, loading both using .45 ACP data without any problems. These are used in two 625-8's (a JM and a PC) along with a 5-screw 1955 Target.

Most are loaded with my standard 230 grain load (LRN, FMJ or plated) over of 5.0 grains of Bullseye. Works well enough for my purposes.

If your getting flattened primers and hard extraction (true signs of high pressure) is there a chance your AR brass is the old "balloon head) cases that actually have less interior space?
I know they have not been made for years but just checking a possible.

Actually, the balloon-head cases have MORE space, not less than solid-head cases.

It probably takes about 40,000 psi to flatten standard large pistol primers, and perhaps 50,000 to make cases start to stick to chambers (assuming cases and chambers walls are within specs). So, those pressure signs (which pertain to rifle pressures, not typical handgun pressures) have no application to the 45 AR, 45 ACP or 45 Colt.

See the second half of post #26 above.

This may be true in guns of recent manufacture but it was not the original intent of the design of the 1917's, M25-2's or the 1950 and 1955 Target .45's. I can't tell you how many old timers I've seen at the range knocking spent .45 ACP cases out of these guns with a short dowel or pencil because the half moon clip then provided with these guns were such a pain in the gazanski to deal with. In the case of the 1917's, the guns needed to operate under combat conditions even if the half moon clips were lost in action. In essence, Smith and Wesson did not go to the expense and trouble to machine the shelves in the chamber of these guns just for grins.

So, it's my understanding that the original design intent of the .45 Auto Rim case was to provide a mechanism to facilitate spent case extraction without the use of half moon clips and not to provide a headspacing index point.

Bruce

No, the rim on the AR does both. It provides a headspacing datum and allows for extraction. That quote is mine. Yes the older 1917s, 625s, etc., like my 625-3,have properly cut chambers that permit headspacing on the case mouth without a moonclip. But when you use ARs in those guns the rounds don't seat quite as deep, so they do in fact headspace on the rim, not the mouth.

BTW,I am one of those oldtimers you see at the range, but I usually don't need a pencil or dowel when I choose to not use a clip or ARs. Just a little shake and they fall right out.

__________________
USAF, 69-92
Vietnam, 72-73

Just as a data point, my newer 625 PC will headspace taper crimped 45acp just fine. It also works with the clips, the 45AR taper crimped, and 45AR that is roll crimped.

Craig

Be very careful about assuming loads are the same in 45 AR. It depends entirely on the brass. Before using ACP loads in AR check every AR case to make sure you don't have any of the old "balloon head" cases in AR. If you do you should weed them out. They will not stand the pressure of modern ACP loads that are close or on the max line.

If you don't know what "balloon head" cases are you will need to do some research so you can recognize them. When you look down in them they are deeper and have a larger case capacity and the rim is fairly weak.l They have not been made in a lot of years. But they were common in AR case construction at one time just as they were also used in 45LC. I still see them once in a while, usually in fired brass, at gun shows.