.223 brass

[steve4102]

WOW, not sure my mind is capable of absorbing all that without help, so I have a few question to help me understand. Sorry if they seem rather stupid.

Are you saying that Factory 223 and factory 5.56 ammunition is running at relatively the same pressures give or take?

If, so are you saying shooting 5.56 ammunition out of a 223 is perfectly acceptable as they are running at the same pressures?

Have you discussed this with Quickload as well. He has the 5.56 running at 62,366psi and the 223 SAAMI running at 55,000psi?

This chart done by Barnes shows that the factory 5.56 ammo operated at about 10K higher then the 223 ammo in the same barrels. How do you explain this?



http://www.luckygunner.com/labs/5-56...a-6%2F26%2F12-

Sorry, I don't want to sound like I disagree,I am just looking for clarification.

[Bart B.]

I'll explain it as simple as possible.

Both were not loaded to the same pressure specs using the same barrel and measuring system. That difference is quite normal across several factory and arsenal rounds shot in the same barrel. And both commercial and military plants may well have a 6,000 psi average difference across several lots.

Too many different measuring tools and test barrel dimensions out there to make any valid comparisons. To say nothing about the tolerances across each component used that will skew the results. That Lucky Gunner link's tests would have been a lot more informative and meaningful had he used 10 different lots of each ammo type then published their numbers. One of each has little statistical significance.

[243winxb]

TECHNICAL DATA SHEET
UNSAFE FIREARM-AMMUNITION COMBINATIONS http://www.saami.org/specifications_...mbinations.pdf

In Firearms Chambered For 223 Remington. Do Not Use These Cartridges. 5.56mm Military,
222 Remington
25-45 Sharps
30 Carbine
300 AAC Blackout

If i have a 223 chamber, i should not shoot 5.56mm Military factory ammo in said chamber?

[243winxb]

CARTRIDGE, 5.56MM, BALL, M855 Chamber pressure ..............55,000 psi http://www.tuffsteel.com/manuals/armyammodata.pdf CARTRIDGE, 5.56MM, BALL, M193 Chamber pressure...............52,000 psi

[steve4102]

Don't forget, military Data sheets use both CUP and PSI interchangeably. For years shooters and handloaders were convince the 7.62 ran at 50K psi while the 308 ran at 62K psi.

[Bart B.]

243win, pressures in that link's document are CUP numbers but have the traditional PSI labels. Real PSI numbers for these two rounds are about 10,000 higher. A never ending point of confusion.

[Unclenick]

Steve4102,

The QuickLOAD numbers are just the published numbers from the two standards systems. The program predicts channel transducer measurements. I will have to ask Hartmut Broemel (QuickLOAD's author) about this cartridge, specifically, because of the confusion, but, in general, IMHO, you want to use CIP numbers as limits with that program because that's what its results were compared to during development. They are much more consistent relative to copper crusher results, than SAAMI's piezo numbers are. They are also easy to look up on line on the CIP TDCC pages. (Just select the category at the top of the page and select the page numbers below. Since they don't put a decimal point in front of calibers, you'll find the metric cartridges listed first, followed by U.S. designations.) You will want to convert from units of bar if you don't use QuickLOAD's convertor. Just multiply bar by 14.5038, I suspect Herr Broemel just included the SAAMI numbers to avoid causing angst.

Again, look at the M193 numbers for the the U.S. military loads them. All the CUP numbers, military (U.S. and NATO) and civilian (SAAMI and CIP) are the same within reasonable statistical sameness. I don't think it is a coincidence that the two (American and European) copper crusher systems are much more alike than their two piezoelectric systems are, both using drilled cases. The U.S. military did upgrade their copper crushers in the 80's, but the standards were unchanged.

That U.S military spec I quoted gives 55,000 psi MAP (by conformal pressure transducer). I suspect the U.S. uses this instrument because they have a lot of ammo made by contractors like Federal and didn't want different instrumentation for quality control purposes. But the ammo produced this way is completely compatible with all 5.56 NATO ammo. The reference ammo loads for setting the standards were supplied by the U.S. to the NATO allies. The U.S. ammo loaded to that SCATP 5.56 55,000 psi standard performs to NATO requirements, just as NATO ammo loaded to the EVPAT 5.56 62,366 psi standard on their equipment is compatible with our military weapons. It produces the same velocities, gas port pressures, and exterior ballistics.

Why would you be warned against using 5.56 mm in a civilian chamber? The NATO chambers have about twice as much freebore. This allows some military specialty ammo to have its ogive further forward of the case mouth than civilian ammo is loaded to, so there is a danger with some specialty ammo of jamming the lands of a tight civilian match chamber, raising pressure about 20%. M193 and SS109 do not have that problem, but all sorts of stuff gets surplused out and into the market. You should check with a bullet ogive registration type seating depth gauge before using 5.56 of questionable origin in your SAAMI chamber.

Why would randomly sampled military ammo shoot warmer than civilian? I've notice that even with 7.62, which, as Bart explained, everyone thought for years was loaded to lower pressure. (That was because only SAAMI published copper crusher pressure in CUP, reserving psi for piezo transducer readings, while the military kept calling both psi. The reader of military specs is simply expected to know what instrument the measurement was taken with.) The reason for the higher pressure in the military ammo is not the measuring system, but that it must meet not only a maximum average chamber peak pressure limit, but also has to produce gas port pressure within a ±pressure window and also has to produce exterior ballistics within a given window to keep NATO allies weapon sight systems and settings for different ranges cross-compatible. These requirements combine to limit not only the peak pressure, but indirectly limit the minimum chamber pressure with current powder technology.

SAMMI does have muzzle velocity ranges for some bullet weights, but they are not mandatory. The military can't load their cartridges down and still meet NATO requirements. Commercial manufacturers don't have that constraint, and have to be compatible with guns with a wide range of ages and that have been subjected to a wide range of maintenance standards, so they have some incentive to minimize pressure and loads where they can. Bottom line, commercial ammo doesn't have to meet the same minimum standards.

Finally, just to show how loopy the pressure measuring is, take a look at the table below. Again, from Ken Green, these are all for the same reference ammunition, identical loads fired in the different measuring instrumentation. These all had original SAAMI MAPs of 52,000 CUP (the reason I selected them). Note how much more inconsistent the ratio of SAAMI CUP to SAAMI psi is, than is the ratio of CIP CUP to psi. It is very consistent. I believe this to be due to the greater similarity of the two CIP test setups. 223 is the odd man out under SAAMI. None of SAAMI's other 52,000 CUP round measure so low on the conformal transducer. I don't know why. The transducer is much more consistent when the same reference load lot is fired at several labs, but consistency and absolute accuracy are not the same thing. Clearly relative rather than absolute pressures are the order of the day here.

Cartridge           SAAMI                    CIP
                CUP         psi        CUP          psi 
223 Rem       52,000      55,000     53,664       62,366
243 Win       52,000      60,000     52,214       60,191      
270 Win       52,000      65,000     53,664       62,366
308 Win       52,000      62,000     52,214       60,191
6mm Rem       52,000      65,000     53,664       62,366
7mm-08        52,000      61,000     51,996       60,191