Quote:
Originally Posted by Sig 210
There are several myths concerning military 5.56mm ammo. It is a myth that US made 5.56mm cases are thicker than commercial cases. For over 40 years I have weighed my cases when real good accuracy is desired. See the link below for case weights.
It is also a myth that 5.56mm military ammo is loaded to much higher pressure than commercial .223 ammo. US military 5.56mm ammo is loaded to 52,000 Psi + 3 standard deviations; not to exceed 58,000 psi. SAAMI specs are 55,000 psi.
SAAMI pressures
BTW: There are at least a dozen different .223 chambers. Unless your rifle is an H@R Handi rifle or it has a tight .223 match chamber there are no problems with firing 5.56mm military ammo in that gun. H@R re-ground their reamers and their chambers are all over the place from huge to very tight.
A gunsmith friend says that he knows of no US firearm maker who currently uses a SAAMI chamber for the .223.
This is a good link to peruse:
AR15BARRELS.COM - Technical Documents |
That's interesting. The two relevant PDFs on that website both indicate a noteworthy variance between .223 Rem and 5.56x45, and even more curiously the second PDF describes a lack of consistency in .223 Rem chamberings compared to in 5.56x45 chamberings. NATO EPVAT testing indicates that 5.56 NATO chambers must be proofed to 62,000 psi. Max pressures for a rifle/ammo combo are to add 25% to the stated pressure, totaling almost 80,000 psi (yes, that's
significantly higher than the lower SAAMI pressures).
I'll give you that
some military ammo is loaded on the higher end of the allowed SAAMI specs, but there's a lot more room for pressure spikes (military concern given the sheer volume of ammo they receive) and reloading errors in NATO chambers than in SAAMI chambers. I'd sooner take the low end of the NATO chamber than the high end of the SAAMI chamber.
-B
__________________
RIP, Jeff Dorr: 1964 - July 17, 2009. You will be missed.
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