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Old 02-12-2008, 06:06 AM
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Pressure vs. caliber


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I'm showing my age again (newbie) but I have a question I have't seen answered in my 2 loading manuals since I now load .45ACP also.
Are overpressure signs in brass similar regardless of caliber or is the amount of pressure absolute? Meaning--- would I see pressure signs on brass in my lowest rated gun, the 45, or would the gun blow up first?
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Old 02-12-2008, 06:55 AM
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First, I think you mean pressure versus cartridge, because caliber only refers to the diameter of the bore. There are some low-pressure cartridges in .45-caliber (your 45 ACP) and some very high-pressure ones (454 Casull). So I'll discuss it as cartridge, with your approval.

The 45 ACP has a top pressure rating that's way below the threshold at which brass deforms, so you are unlikely to ever see any "traditional pressure signs" in a 45 ACP unless you have exceeded the maximum cartridge rating by two or three times. Furthermore, the very short duration of the pressure curve in that cartridge means that due to "lag time" even the thin metal in the primer cup doesn't have time to react to the pressure before the pressure has already dropped. Combine that wit the slam-bang of the action in a 45 ACP pistol, and you cannot "read" the primer for pressure signs, either.

All that means that if you did wildly exceed the pressure rating for the 45 ACP, you might damage the gun before or simultaneously with cartridge deformation. I doubt you'd have the gun blow up, but you might deform the barrel locking lugs, the lug seats in the slide or something like that.

It's also possible that you could burst a case, especially in a barrel with an unsupported chamber. But that's not the same as the traditional pressure signs, which assume a fully supported case.

The short answer is that handguns are very different from rifles, and don't readily allow for the "tea leaves" approach to pressure estimation.
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Old 02-12-2008, 08:03 AM
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If you're trying to find ways to judge pressure in the 45 ACP, Rocky's shown you why traditional methods used on rifle ammo won't work. Probably your best pressure indicator in a 45 auto is case ejection.
If you get some factory 230 ball, and some factory wadcutters, fire them and watch the ejection- the 230 ball will throw the brass farther than the light wadcutter load. If some of your handloads are flinging brass farther than the 230 ball factory, you have a high pressure load, and should reduce your powder charge.
Not an exact science, but it's about all you have to go by.
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Old 02-12-2008, 09:21 AM
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Thanks, that's what I suspected. It didn't seem possible that different guns with different rated pressures would leave the same signs. I didn't want to develop a false sense of security inspecting brass.
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Old 02-12-2008, 05:21 PM
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Pressure in handguns is a very different game than pressure in rifles.

With handguns, you can split the game into revolvers and autos.

Revolvers can be classed as Ruger Single action/Freedom Arms, or Smith class, or less. IMO. Don't even think that a M629 will take the kind of heat that a Super Blackhawk, or Redhawk will. I love both.

With Autos, you need to be way more refined than a Revolver shooter.

Mixing brass on a 9mm load can produce everything from a near dud, to a serious bomb, all with tye same primer/bullet/case. Weigh a few cases sometime. What's mild in one case, may damage the frame in another. In a .45, pressures that flatten a primer, mean you're close to a life threatening event.

Start low and work up, use a chromograph, never mix cases, trim to spec. You will be safe. Never take a max load for one set of conditions, and apply it to another bullet/case/primer of "equal" or similar specification.

With handgun loads, loading conservative will assure a long(er) career.
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