Archie said:
"I cannot puzzle out how there are two firearms which use the same ammunition and two different chamber pressure maximums."
The cartridge we are discussing is only one example. If a firearm can shoot .45 Auto Rim, it likely can shoot .45 ACP.
Not exactly. No firearms are chambered and designated for use with the .45 Auto Rim cartridge. They are all chambered and designated for the .45 ACP round. The Auto Rim case was designed as a convenience, not an alternative.
BUFF said:
There are lots of others. The .38 ACP and the .38 Super; one led to the other.
Again, not exactly. The .38 ACP and the Super .38 are two different rounds - even though they use the same case. (I've often wondered why Colt ever did such a thing. Lawsuits and all.)
BUFF said:
My .357 Magnums can shoot .38 Specials. The Magnum round was developed from the Special round.
Not at all. The Magnum round was designed as a high pressure round and the makers extend the case .125" to make sure the higher pressure round doesn't fit into the lower pressure rated arm.
BUFF said:
In a way, the Auto Rim round was developed from the ACP round. Two cartridges, same gun.
Yes; they are both designed to be fired in a .45 ACP chamber. The Auto Rim is far more convenient to use in a conventional, double action, revolver. However, adding the flange does not weaken either the case or the arm. There exists no safety reason to down load the AR case.
By the way, you forgot to mention the problem between 9mm Parabellum and 9mm Glisenti. Same size as 9mm Parabellum, loaded to more or less .380 ACP pressures. They are different cartridges and intended for different pistols.
BUFF said:
Perhaps you don't understand what "SAAMI specs" really means.
Yes, I do.
Archie said:
"If by that statement you mean the load 'maximums' which imply .45AR is NOT to be loaded to the same velocities as .45 ACP..."
BUFF said:
No, I didn't say or mean that at all. What I meant was that SAAMI recommends that factory loadings of various cartridges not exceed certain pressures, primarily for safety's and compatibility's sake.
I understand what you wrote. Perhaps you do not understand with the powders available at the time the .45 Auto Rim was introduced, pressure and velocity were tightly linked. One could not reduce pressure without reducing velocity - in this specific example. Furthermore, the pressure level of the .45 Auto Rim was not reduced 'for safety's sake'. One notes SAAMI - or anyone else - did not ever issue a warning about shooting surplus G.I. ball .45 ACP ammunition in any revolver so chambered. (Or did I sleep through that?)
BUFF said:
There is, so far, no system available to the home ammo loader to measure their loads' pressures.
Yes, there are. I have two such devices.
BUFF said:
It is just a curious fact that SAAMI had put .45 Auto Rim's maximum recommended pressures lower than their own standard for .45 ACP. The developer of the .45 Auto Rim, the Peters Cartridge Company in 1920, used a lead instead of a jacketed bullet. It is just a guess on my part, but I bet that SAAMI's maximum pressure recommendation for the Auto Rim was probably based somewhat on measuring the pressures of the ammo company's existing product.
I believe I mentioned that possibility. The SAAMI limits effectively are set to duplicate the initial Peters loading, not the .45 ACP for which the arm is chambered and designed. I have no idea why; not only did they not ask me, they didn't even notify me they were in the process!
BUFF said:
Frank Barnes' tome "Cartridges Of The World" says that the developer of the Auto Rim used a lead bullet to reduce wear to the rifling of the guns' barrels. The rim was just added to make use of the revolvers chambered in .45 ACP more convenient, he wrote. He also wrote that any load safe in the .45 ACP "can be used in the Auto Rim with about the same results."
I just looked at CoTW. Yes, it confirms - at least repeats - the old theory the lead bullet was to reduce rifling wear.
I don't find the statement about 'safe loads' in CoTW #14; BUT I did find it appended to the loading data/factory loads chart in CoTW #8! The statement seems to have been left out in later editions. (Lawyers, maybe?) I fully concur with the thought. Why identify and chamber the revolver for use with .45 ACP ammunition, then expect no one would fire that ammunition?
BUFF said:
Other than this, I don't know how to reply to your post because I don't understand what you are trying to say.
Humpff? I thought I was pretty clear. A handgun chambered for .45 ACP and expected by both the manufacturer and owner - the U. S. Army - to fire standard .45 ACP ammunition should be considered safe to use reloaded ammunition suitable for .45 ACP pistols.
And modern made revolvers manufactured for .45 ACP - like the Smith & Wesson Model 1955 Target Revolver - should handle .45 ACP pressure levels without serious comment.
I do - in the manner of prudent handloaders for many, many winters - start at the low end of the load weight/pressure/velocity loading and work up until the velocity and accuracy is suitable or I reach the maximum load with the dire warnings.
I'm just a bit puzzled by your remarks, BUFF. You seemed to disagree with my thoughts, then you cited information confirming my methods and theories.
Oh. I'm not the first one to push the .45 Auto Rim up from the erstwhile factory pressures and velocities. One of the 'annuals' - and my brain has a drive belt slipping again - had an article called "Forgotten, but not gone!" and offered an essay on the .45 Auto Rim being loaded to the upper end of the acceptable spectrum.