Thread: 5.56 and .223
View Single Post
Old September 3, 2012, 07:41 AM   #6
Bart B.
Senior Member
 
Join Date: February 15, 2009
Posts: 6,318
Interesting stuff on this in:

http://www.thegunzone.com/556v223.html

SAAMI's concerns are based on the chamber and cartridge dimensions, when there's the least difference in given cartridge and chamber sizes. Maximum spec 5.56 round in a minimum spec .223 chamber and bore can raise peak pressures higher than SAAMI feels is safe. That's based on the pressure issues SAAMI is concerned about.

So, as with all other product safety warnings and issues, one gets to decide their own margin of safety, then do whatever they feel is best for their objectives. It's my opinion that most folks reload belted "magnum" cases to a greater peak pressure over SAAMI specs than what 5.56 NATO rounds will have in .223 Remington chambers.

In comparing MIL SPEC pressure for the 5.56 M193 round to the SAAMI one for .223 Rem. SAAMI specs for the .223 max. average pressure are 52,000 CUP and 55,000 PSI. But the maximum average sample mean pressure for the .223 is 55,300 CUP, 58,300 PSI.

From MIL-C-9963F MILITARY SPECIFICATION: CARTRIDGE, 5.56MM, BALL, M193 (15 OCT 1976)Note "PSI" in MIL-C documents is actually CUP numbers; the military uses that term for copper crusher gauge units of pressure.
3.7.1 Measurement by copper-crush cylinder.-The average chamber pressure
of the sample cartridges, conditioned at 70° ± 2°F, shall not exceed
52,000 pounds per square inch (PSI). The average chamber pressure plus
three standard deviations of chamber pressure shall not exceed 58,000 PSI.
3.7.2 Measurement by piezoelectric transducer.-The average chamber
pressure of the sample cartridges, conditioned at 70° ± 2°F, shall not
exceed 55,000 PSI. The average chamber pressure plus three standard
deviations of chamber pressure shall not exceed 61,000 PSI.
Bart B. is offline  
 
Page generated in 0.03532 seconds with 8 queries