Tiered pressure ranges and modern specs

Ok.. some people are confused about CUP & CIP. CUP is Copper Units of Pressure & is a pressure reading much like PSI, etc. CIP is the “Commission Internationale Permanente” it is NOT a pressure reading, but rather the European equivalent of SAAMI, which deals with the specs on everything firearms, including Chamber, Case & Ammunition specs. They are NOT the same thing. You cannot convert PSI to CIP, as CIP is not a measurement. Nothing said here had anything to do with using or converting specific measurements, but rather the difference between SAAMI(UNITED STATES) & CIP (Europe)

Hope that helps.

David Hoback said:

Too many Snowflakes & Lawyers involved with SAAMI I think.

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It's generally the opposite, actually... CIP seems far more cautious and technocratic than SAAMI. CIP also has legal force, manufacturers can't sell cartridges or rifles that have not been CIP approved. So something like the 280 AI, or any other non-CIP-approved round, is not commercially available in Europe. Lots more rules about everything. For example:

"I was looking at the possibility of building a .38AMU clone but, here in Belgium, we have to send our firearms to the Proofhouse. If the caliber is not CIP-approved...not proofing is available and, legally, you cannot shoot a firearm not proofed (I was the first in Belgium to build a .300Blk carbine...I had to have it proofed as a .300Whisper)."

It’s certainly not every cartridge, but look at many of the most popular.

http://kwk.us/pressures.html

Thanks, I lost my link to that list.

David Hoback said:

Ok.. some people are confused about CUP & CIP.

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But I am not one of them.

There are three main types of chamber pressure instruments; crusher, strain gauge, and piezoelectric transducer. I haven't heard of a major industrial user of strain gauges, that seems to be a hobby or small company approach.

There have been others, the Powley P-Max operated on recoil, of all things, and there was a device which imbedded a sensitive insert in the cartridge head itself, to be read on the fired case, out of the gun, by an external meter, no gun modifications required. Both were short lived in the market.

There was a shop with an axial gauge like old British practice, you could send in your own barrel and ammo to know the actual characteristics you were getting, with no worry about an ammo company's PV barrel differing from a conventional rifle's.

There are multiple standard setting organizations, SAAMI in the US, CIP has apparently taken over all the previously independent European proof houses and their national proof laws. Then there are Army and NATO methods and standards.

So you can find a lot of different numbers representing the chamber pressure of one particular load.
Looking in Lyman 49 I see both CUP and psi. In fact for some cartridges like 7mm Remington Magnum, I see both in the same table.
Frex, a 168 gr Sierra + 64 gr IMR 4831 = 2915 fps @ 60,500 psi. But 65 gr H4831 = 2971 fps @ 52,000 CUP.
These are both maximum loads for those particular powders by the method tested, the actual numbers don't matter, they were not arrived at the same way.
So what? I can't measure them anyhow.
But the powder charges do matter. I will not likely exceed the maximum and might even stop short if I get better accuracy or "pressure signs" short of the maximum.

Then you get into "load shopping." My old Sierra manual stops at 62.2 gr IMR 4831 for that bullet, but goes up a smidgen to 65.6 gr of H4831.
So which is "right?"
How about those old manuals with the Good Stuff? A lot of their loads were reached by eyeballing brass and primers and maybe by stopping when they had factory velocity or a little more, just like you can.

I think that’s how any experienced Reloader does it. They may start with a loaf manual for various powders/bullets, etc., but will reach their own Max loads for velocity, & accuracy loads based on their own findings. And many of the numbers may contradict a load manual. I know I certainly do. I study my brass post firing. I also encourage those new to reloading as well…learn pressure signs. Know them through & through.

Dave DeLaurant said:

Here's a photo of the respective bullets M1906, M1 and M2 ball ammunition for comparison:

View attachment 1108509

If Wikipedia has it correct (for once), there was also a different propellant specified for each of these three cartridges.

I believe the muzzle energy and pressure curve remained essentially the same with M1 and M2 ball, since the M1 rifle was developed during the heyday of M1 ball ammo. Perhaps the term 'ballistically downrated' would be more correct than 'downloaded'?

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At one point all three were loaded with the same powder... IMR 1185.

M1 ball wasn't ballistically "downrated" to M2 ball. It was a whole new round. Or more correctly an updated/improved M1906 loading. IMR 4895 didn't make a showing in USGI ammo until '43-44 time frame. Up until then it was IMR 1185 or IMR 4676.

M1 ball always made it's spec. Every bit I've tested (from 1927 to 1940) is basically 2700 fps +/- 30 at the muzzle. It's ALWAYS been more accurate than M2 ball as well.

Jim Watson said:

Thanks, I lost my link to that list.

But I am not one of them.

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Oh… no Jim, I wasn’t referring to your posts. Sorry if you thought I was.

I know you’re baggin’ what I’m rakin’ partner. And I am surely smellin’ what you’re steppin in.