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You can purchase a copy of the US Army SCATP test procedures here: http://standards.globalspec.com/std/1835971/army-scatp-5-56and here: https://global.ihs.com/doc_detail.cfm?document_name=SCATP%205.56&item_s_key=00093161"show a link that says military ammo is 223 pressure spec." OK, how about text from the actual spec itself? Paragraph 3.7 being the one of interest: MIL-c-63989C(AR) 15 February 1994 SUPERSEDING MIL-c-63989B(AR) 25 September 1991 MILITARY SPECIFICATION CARTRIDGE, 5.56MM, BALL, M855 This specification is approved for use by the U.S. Army Armament, Munitions and Chemical Command, and is available for use by all Departments and Agencies of the Department of Defense. 1. SCOPE 1.1 Scope. This specification covers the M855 Ball cartridge for use in 5.56mm weapon systems with a “one in seven” (one revolution in seven inches) barrel twist (see 6.1). ... 3.7 Chamber pressure. The average chamber pressure of the sample cartridges, conditioned at 70° + 2°F shall not exceed
55,000 psi. Neither the chamber pressure of an individual sample test cartridge nor the average chamber pressure plus three standard deviations of chamber pressure shall exceed 61,000 psi. ...
Coyote Hunter - NRA Patriot Life, NRA Whittington Center Life, GOA, DAD - and I VOTE!
No, I'm not a Ruger bigot - just an unabashed fan of their revolvers, M77's and #1's.
A good .30-06 is a 99% solution.
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After writing my last post, I found an updated version of the MIL-spec. http://quicksearch.dla.mil/Transient/74410E9F151846288451A5048FF039AF.pdfhttp://quicksearch.dla.mil/Analyse/ImageRedirector.aspx?token=251894.31482 "MIL-C-63989C (AR) AMENDMENT 4 30 January 2001 SUPERSEDING AMENDMENT 3 15 October 1999" Paragraph 3.7 is changed as follows, which increases the maximum average pressure to 58,700 PSI. This is neither the SAAMI .223 spec nor the NATO spec. "3.7 Delete in its entirety and substitute the following: 3.7 Chamber pressure. The average chamber pressure of the sample cartridges, conditioned at 70 degrees plus or minus 2 degrees F, shall not exceed 58,700 psi. Neither the chamber pressure of an individual sample test cartridge nor the average chamber pressure plus three standard deviations of chamber pressure shall not exceed 64,700 psi."
Last edited by Coyote_Hunter; 02/27/17.
Coyote Hunter - NRA Patriot Life, NRA Whittington Center Life, GOA, DAD - and I VOTE!
No, I'm not a Ruger bigot - just an unabashed fan of their revolvers, M77's and #1's.
A good .30-06 is a 99% solution.
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More searching found this explanation as to why C.I.P/NATO 62,366 PSI equals SAAMI 55,000 PSI. Which is different than saying 55,000 PSI equals 62,366 PSI. Kind of like comparing PSI and CUP. https://en.wikipedia.org/wiki/5.56%C3%9745mm_NATO
Pressure[edit]
C.I.P. defines the maximum service and proof test pressures of the .223 Remington cartridge equal to the 5.56mm NATO, at 430 MPa (62,366 psi). This differs from the SAAMI maximum pressure specification for .223 Remington of 380 MPa (55,114 psi), due to CIP test protocols measuring pressure using a drilled case, rather than an intact case with a conformal piston, along with other differences.[52] NATO uses NATO EPVAT pressure test protocols for their small arms ammunition specifications.
Because of these differences in methodology, the CIP pressure of 430 MPa (62,366 psi) is the same as a SAAMI pressure of 380 MPa (55,114 psi), which is reflected in US Military specifications for 5.56mm NATO, which call for a mean maximum pressure of 55,000 PSI (when measured using a protocol similar to SAAMI).[53]
These pressures are generated and measured using a chamber cut to 5.56 NATO specifications, including the longer leade. Firing 5.56mm NATO from a chamber with a shorter .223 Remington leade can generate pressures in excess of SAAMI maximums.
Coyote Hunter - NRA Patriot Life, NRA Whittington Center Life, GOA, DAD - and I VOTE!
No, I'm not a Ruger bigot - just an unabashed fan of their revolvers, M77's and #1's.
A good .30-06 is a 99% solution.
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Campfire Ranger
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That's really convoluted..........but what I do know for sure is that genuine 5.56 MIL-Spec ammo such as IMI chronos faster than commercial 223, like PMC Bronze.
And in some guns, I will get short stroking or failure to lock back with 223 ammo, not with the 5.56.
Thanks for doing the look-ups; interesting info that can easily be taken out of context.
MM
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It's not just how hot the ammo is loaded. Try some 77 gr. Mk262 in your short throat .223 chamber. My guess is you would see higher pressure. I would assume (and I may be wrong) that SAAMI spec .223 ammunition is tested in a shorter throated .223 chamber and 5.56 NATO is tested in a longer throated 5.56 chamber. So the comparison is not apples to apples. Western Powders data for TAC powder and a Hor. 55gr. BT-FMJ bullet: .223 Max Pressure 54,894 psi 5.56 Nato Max Pressure 61,335 psi Western Powders Load Data Not sure what the debate is about.
Let's Go Brandon! FJB
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It's not just how hot the ammo is loaded. Try some 77 gr. Mk262 in you short throat .223 chamber. My guess is you would see higher pressure. I would assume (and I may be wrong) that SAAMI spec .223 ammunition is tested in a shorter throated .223 chamber and 5.56 NATO is tested in a longer throated 5.56 chamber. So the comparison is not apples to apples. Western Powders data for TAC powder and a Hor. 55gr. BT-FMJ bullet: .223 Max Pressure 54,894 psi 5.56 Nato Max Pressure 61,335 psi Western Powders Load Data Not sure what the debate is about. You hit the nail on the head. It doesn't matter whether 5.56 ammo in a 5.56 chamber is loaded to higher pressure than 223 in a 223 chamber, that's not the point. It does matter that when 5.56 and 223 are fired in the same chamber, 5.56 is unarguably hotter. Why some insist on debating this I don't know.
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OP - sending a PM on your OEM II question, easier than watching the thread go off the rails.
Last edited by AH64guy; 02/28/17.
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OP
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OP - sending a PM on your OEM II question, easier than watching the thread go off the rails.
I really appreciate that AH, I didn't want to interrupt the intelligent/technical conversation the boys had going 
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It's a good peek behind the curtain at some of the personas you are getting into.
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Campfire 'Bwana
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Campfire 'Bwana
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All you have to do is look at a loading manual.
Western lists loads for both the .223 and 5.56, with the average max load for the 5.56 exceeding the .223 load by 1.5 grains.
Anyone who thinks adding an extra 1.5gr of powder to a case with 30gr of H20 capacity doesn't cause an increase in pressure needs to sell their guns and take up golf.
Last edited by antelope_sniper; 02/28/17.
You didn't use logic or reason to get into this opinion, I cannot use logic or reason to get you out of it.
You cannot over estimate the unimportance of nearly everything. John Maxwell
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Campfire 'Bwana
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It's not just how hot the ammo is loaded. Try some 77 gr. Mk262 in you short throat .223 chamber. My guess is you would see higher pressure. I would assume (and I may be wrong) that SAAMI spec .223 ammunition is tested in a shorter throated .223 chamber and 5.56 NATO is tested in a longer throated 5.56 chamber. So the comparison is not apples to apples. Western Powders data for TAC powder and a Hor. 55gr. BT-FMJ bullet: .223 Max Pressure 54,894 psi 5.56 Nato Max Pressure 61,335 psi Western Powders Load Data Not sure what the debate is about. You hit the nail on the head. It doesn't matter whether 5.56 ammo in a 5.56 chamber is loaded to higher pressure than 223 in a 223 chamber, that's not the point. It does matter that when 5.56 and 223 are fired in the same chamber, 5.56 is unarguably hotter. Why some insist on debating this I don't know. Because some people are so stupid they need to sell their guns and take up golf.
You didn't use logic or reason to get into this opinion, I cannot use logic or reason to get you out of it.
You cannot over estimate the unimportance of nearly everything. John Maxwell
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