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SAA Clones: Why higher 45 ACP pressures but...
- Thread starter LivewireBlanco
- Start date
Kilibreaux
New member
There is a difference between psi - pounds per square inch, and TOTAL pressure applied!
A .45 ACP top load is in the 20-21K range and even THAT is above SAAMI spec.
The total pressure exerted by a .45 ACP does not exceed the total pressure of any .45 Colt load.
A .45 ACP top load is in the 20-21K range and even THAT is above SAAMI spec.
The total pressure exerted by a .45 ACP does not exceed the total pressure of any .45 Colt load.
It's just a guess but I think the original .45 colt rounds were black powder.
Correct. The 45 Colt load was developed in the early 1870's. A good bit before smokeless was being used in any commercial handgun loads. The original load was 40 grains of black powder and a 255 grain bullet.
Bingo!If you want a -SIMPLE- answer (and yes, one with the truth behind it) it's quite simply that it's a huge world of liability for the manufacturer to ever go that route, with almost ZERO payoff for them.
What???The total pressure exerted by a .45 ACP does not exceed the total pressure of any .45 Colt load.
The history of the .45 colt and the reason the for manufacturer's loadings is irrelevant to the poster's original question. He wondered why: If the .45 ACP is safe at 21000 psi, then why couldn't HE LOAD (handload) the .45 colt to 21000 psi safely in the same frame and with two cylinders of the same steel and diameter? "Sevens", "mavracer", "Tmsr", and "rclark" all had the answer right: You can. Handloader magazine has an article with 23,000 psi loads for the mid-frame ruger, which I assume would be compatible with a modern colt or USFA revolver.
As "savit260" hinted, there is a difference between chamber pressures and resulting muzzle velocity for the two cartridges. At 21000 psi, a .45 ACP will drive a 230 bullet at around 850 ft/sec. At 23,000 psi, a .45 colt will drive a 250 grain bullet at around 1100 ft/sec. That will translate into a huge difference in recoil and a huge difference in battering and wear on your revolver. Personally, I would save the heavier .45 colt loads for a larger frame revolver.
Another thing to note, although I don't know if it is significant, is that the .45 ACP cartridge is about .004 in. smaller is diameter than the .45 colt. (.476 vs .480). That would mean that the metal between the cylinder holes is .004 inch thinner in the .45 colt cylinder.
@44flattop: "Kilibreaux's" statement puzzled me too. The only thing that made sense to me is that since the peak pressure will drop quickly after the bullet leaves the cartridge, then the total pounds-force exerted against the cylinder walls will be different for each cartridge due to the different cartridge lengths, based on peak chamber pressure. If that was what he was trying to say, then that's an easy calculation. Just multiply the chamber pressure times the outside area of the cartridge to get the total force. And if you do the calculations, the total force against the cylinder is about the same for both cartridges at SAAMI specifications. (Actually the total force from the .45 ACP is about 2% higher.) However, I'm not sure I see the point. The load will be distributed and all that should matter would be the force per unit of area.
As "savit260" hinted, there is a difference between chamber pressures and resulting muzzle velocity for the two cartridges. At 21000 psi, a .45 ACP will drive a 230 bullet at around 850 ft/sec. At 23,000 psi, a .45 colt will drive a 250 grain bullet at around 1100 ft/sec. That will translate into a huge difference in recoil and a huge difference in battering and wear on your revolver. Personally, I would save the heavier .45 colt loads for a larger frame revolver.
Another thing to note, although I don't know if it is significant, is that the .45 ACP cartridge is about .004 in. smaller is diameter than the .45 colt. (.476 vs .480). That would mean that the metal between the cylinder holes is .004 inch thinner in the .45 colt cylinder.
@44flattop: "Kilibreaux's" statement puzzled me too. The only thing that made sense to me is that since the peak pressure will drop quickly after the bullet leaves the cartridge, then the total pounds-force exerted against the cylinder walls will be different for each cartridge due to the different cartridge lengths, based on peak chamber pressure. If that was what he was trying to say, then that's an easy calculation. Just multiply the chamber pressure times the outside area of the cartridge to get the total force. And if you do the calculations, the total force against the cylinder is about the same for both cartridges at SAAMI specifications. (Actually the total force from the .45 ACP is about 2% higher.) However, I'm not sure I see the point. The load will be distributed and all that should matter would be the force per unit of area.
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LivewireBlanco
New member
Ok, so just for an example...since Lyman and others don't publish their pressure for most 45 Colt loads, does anybody know what load would be at that 21,000 psi limit? I read the Handloader about the different loads and one of them had 9-10 grains of Unique pushing the 270 gr RCBS bullet in the second category. Am I reading that correctly?
@livewire: I'm looking at "Handloader" No. 275, Dec 2011, which has the loads for the mid-frame ruger. I don't see the specific load you referenced on either table II or III.
It'a sort of interesting how in a later handloader issue (#285, August 2013), Dave Scovill talks about the use of .45 colt +P loads in mid frame rugers and modern colts and recants on the use of +P loads in those revolvers. The objection was not so much that the cylinder would burst and the top strap peel back like a banana, but rather excessive wear and tear on the revolver. What makes me even more cautious is that we are discussing the use of +P's in a uberti. And I'm not knocking uberti's. I have one in .44-40 and I love it. It's just that there are more unknowns with a foreign made gun and less accountability. (Try suing a foreign corporation.) If it were me I would stick with the standard pressure .45 colt loads.
It'a sort of interesting how in a later handloader issue (#285, August 2013), Dave Scovill talks about the use of .45 colt +P loads in mid frame rugers and modern colts and recants on the use of +P loads in those revolvers. The objection was not so much that the cylinder would burst and the top strap peel back like a banana, but rather excessive wear and tear on the revolver. What makes me even more cautious is that we are discussing the use of +P's in a uberti. And I'm not knocking uberti's. I have one in .44-40 and I love it. It's just that there are more unknowns with a foreign made gun and less accountability. (Try suing a foreign corporation.) If it were me I would stick with the standard pressure .45 colt loads.
LivewireBlanco
New member
Yeah, I'm looking into a Ruger New Blackhawk as we speak. Would you say 8.5 gr of Unique pushing a Lee 255 gr lead RNFP would be an acceptable top load?
@ livewire: Thanks to the american bar association, I try not to recommend or list specific powder charges that I use. However, if you look in the speer reloading manual # 14, it shows 8.5 grains of unique and a 255 grain cast SWC, as an acceptable 14000 psi standard pressure load. They indicate that load develops 846 ft/sec in a 5.5 inch colt revolver.
It sounds like you are a fan of unique. So am I, although unique now seems to have an "old timers", or "old school" cachet about it. I like it because it is so versatile and that means stocking fewer powders. I can use unique for .25 ACP to .45 ACP and for revolver mid-range loads from .32 H&R to .45 colt. Plus it works for my 20 and 28 gauge shotgun.
The only problem with unique in the .45 colt is that the case is so cavernous, that you need to carefully check the powder levels in the charged cases to make sure you didn't throw a double charge.
It sounds like you are a fan of unique. So am I, although unique now seems to have an "old timers", or "old school" cachet about it. I like it because it is so versatile and that means stocking fewer powders. I can use unique for .25 ACP to .45 ACP and for revolver mid-range loads from .32 H&R to .45 colt. Plus it works for my 20 and 28 gauge shotgun.
The only problem with unique in the .45 colt is that the case is so cavernous, that you need to carefully check the powder levels in the charged cases to make sure you didn't throw a double charge.
LivewireBlanco
New member
Right on. I'm just trying to be cautious about these max loads since the 45 Colt is a unique cartridge in its age and pressures it can or can't take. I'll stop with 8.5 gr in the Uberti. Thanks everyone!
Yes, for any modern or post 1900 Colt SAA.Would you say 8.5 gr of Unique pushing a Lee 255 gr lead RNFP would be an acceptable top load?
I DID NOT READ ALL THE POSTS HERE, but one of the reasons is this, the 45ACP cylinder is stronger because it is not nearly as long in the chamber as the 45COLT. There is flatout more steel in the 45ACP chamber and yes, it for damn sure does matter !
Huh?
Since both have chambers bored to identical diameters, where is this "more steel?" Am I missing something?
Weakest spot is the bolt notch where its thinest. making the thickest part thicker won't help the weakest link.THE 45ACP CHAMBER is shorter, therfore more steel in the cylinder right where pressures peak in that cartridge.
Think of it this way... A manufacturer may have to spend a little more money properly heat treating the 45 ACP cylinder to meet SAAMI specs, and at the same time not have to go through the same steps for the 45 Colt cylinder due to it's lower pressure tolerance.
The wall thicknesses may be the same, but I for one wouldn't bet that they're the same strength.
The wall thicknesses may be the same, but I for one wouldn't bet that they're the same strength.
There are still a lot of old iron Colt and other brand revolvers around for cartridges like the .45 Colt and .44-40, and even aside from the personal injury aspect and lawsuits, no ammo maker or publisher of reloading data wants to be responsible for a load that blows an antique revolver all over the map.
Jim
Jim
CIP (the European equivalent of SAAMI) has a maximum pressure for .45 Colt at about 16000 psi. That's a nice step up from SAAMI's 14000, and it should be safe in any modern revolver.
I've shot quite a few 25000 psi .45 Colt loads in a 7.5" Ruger Bisley-Blackhawk. That's a heavy gun, and they're still a handful. I would not shoot loads like that in a smaller lighter gun whether it's safe or not. (maybe I'm a wimp)
I've shot quite a few 25000 psi .45 Colt loads in a 7.5" Ruger Bisley-Blackhawk. That's a heavy gun, and they're still a handful. I would not shoot loads like that in a smaller lighter gun whether it's safe or not. (maybe I'm a wimp)
THE 45ACP CHAMBER is shorter, therfore more steel in the cylinder right where pressures peak in that cartridge.
That would still be the case with the .45 Colt. The step in the chamber would be a little further forward, but the thickness beyond that would increase, as you say, where pressures peak.