Shooting .223 in a 5.56 rifle

[barnbwt]

The external dimension are, but the internal dimensions are not. True 5.56 brass is thicker, and every reloading manual will tell you to reduce .223 Rem loads when using military 5.56 brass to avoid exceeding max pressure.

I've heard the same claim with regards to 308 vs. 7.62x51, when we all know they are exactly the same thing, with the NATO round being short-hand for a specific set of pre-approved loads that fall within the 308 standard.

Fun fact; the web article that came up with the super-scary 71ksi figure and all the theories for why this matters so much, just happened to be selling a service to bring '223' chambers into compliance with NATO standards. The psi measurement used for standardization is just that; an arbitrary standard, whose measurement technique and consistency is far more important than exactly how high pressure might actually reach, measured other ways. The whole point of SAAMI is that, a certain cartridge/chamber combination, which when fired to reach a certain pressure measured a certain way, will function safely. Not saying they're full of it, but rather that the whole issue is more overblown than it deserves, precisely because 'non-engineers' would rather pay for a different combination of numbers to be stamped on the outside than understand what is happening. Any number of gun products operate on the same principle of playing off the fears of the ignorant (lubes are probably the worst offenders )

A tight chamber raises pressures; doubtless. A tight chamber can happen with any spec, and does happen with every mass-produced chambering. Same thing for oversize brass (do you mic every round you shoot to make sure the shoulders were placed properly? After all, we're all so paranoid about headspace; how much variance do you think manufacturers here and beyond have lot to lot, maker to maker? If a .003" headspace variance is life-critical, wouldn't the same hold for the brass?). I also wonder how many folks have bothered to slug their barrels, let alone do chamber castings; chrome lining variances could easily make the bore tighter than necessary, causing pressure spikes in guns used exclusively with jacketed ammo.

In summary, lots of things can go wrong, and the numbers "5.56" don't actually change that. I will second calls for evidence to be brought out showing that "223" stamped chambers sold commercially have consistently short leades and tight throats to a degree that would impact anything other than accuracy (the term is a "match chamber" when a tight chamber is a 'feature'). Everyone involved in gunnery knows the rounds are so similar that people can and do shoot them interchangeably; why would you not verify a commercially sold rifle was safe to do this in (even if you won't endorse the practice)? Can someone mic some 223/5.56 rounds from the same manufacturer and see if they're even using different tooling besides the headstamp die? If not, that would lead me to draw some conclusions about what barrel makers are likely doing...

If rounds are not engraving on lands, or wedging into the action, how could "tightness" possibly be affecting anything? Does a few thou of lacquer buildup at the neck cause a kaboom? Not in any significant number. Are your 5.56 cases losing all their primers to cratering, pierces, or loose pockets when fired from a 223? If not, what are those supposed scary pressures doing?

TCB

 

[DJnRF]

I've heard the same claim with regards to 308 vs. 7.62x51, when we all know they are exactly the same thing, with the NATO round being short-hand for a specific set of pre-approved loads that fall within the 308 standard.

Fun fact; the web article that came up with the super-scary 71ksi figure and all the theories for why this matters so much, just happened to be selling a service to bring '223' chambers into compliance with NATO standards.

The mention of claims about the .308 vs 7.62 are exactly opposite of the
ballistic testing of the .223 vs the 5.56. The difference between the .308 and
the 7.62 are reversed from that of the .223 and 5.56 ammunition.

In the case of the 7.62 it actually calls for a smaller chamber size leade than
the .308. It is perfectly alright to fire 7.62 in a .308 rifle. Even the chamber
pressure of the 7.62 is lower than that of the typical factory round of the .308.
For the 7.62 the standard chamber pressure was held at the typical 50,000
pounds just as was the 30-6 ammunition fired in the M-1 rifle and 30 cal.
machine guns. Even the civilian 30-06 ammunition were exactly the same
overall dimensions as the military, even though the pressures were, at times,
more.

I have a .303 Enfield Mk 1. The problem exists with the .303 that five
different rounds were made for the .303 by the British. I have to 'slug'
my chamber to insure it is safe to fire with any .303 ammunition. When
I reload I can then insure I have the right ammo. Otherwise, I could have
a problem if I do not check my rifle first. The fact that I got this rifle many
years back, and that it only was fired with the ammo that had come with
it doesn't give me any information to be sure of anything.

As for the mention of a web site of a company that wanted to sell "a service to bring '223' chambers into compliance with NATO standards." I am totally
unaware of that article. In fact, my information came from a report by the
U.S. Army Ballistic Research Laboratory, Vulnerability/Lethality Division.
Recently, I also read an article on this in The Firearm Blog. My first info on
this was about a year back from the Army Lab.

One thing I have also heard, but since retired have not contacted any of
the manufacturers to confirm, is that many (possibly most) have started
making their .223 rifle chambers to the specs required for the firing of the
5.56 ammunition. In years past when I was in this business I would have
contacted all of the manufacturers of barrels for the .223 to verify this
information. Each of you skeptics, naysayers, and anyone else who would
like to insure their rifle is made with a chamber to fire the 5.56 ammo
safely should also contact the maker of your rifle barrel. I would never let
myself be so ignorant to not insure I have a rifle safe to fire any ammo
claimed to be 'the same'.

In my case here I only have one rifle that fires the same caliber. I am
certain that it has the military barrel as it was one made just for that
purpose. However, any of you that has a .223 rifle that was not specifically
made for the military NATO specs should contact your barrel maker to be
sure of what you have. Don't let yourself be so much of a nincompoop that
you would rather just continue on in a forum to hear yourself make dumb
claims about anything that can involve your own safety, and the safety of
others.

I have stated only facts in here without insisting anything specific about
any particular rifle, or manufacturer. Just facts of the reports, and facts
cannot be changed. Instead, they must be verified. In the particular case
of any claim made about a specific part (such as the barrel in this case),
it behooves each individual to verify the matter for their own safety and
protection from possible harm. Never take the word of a 'nincompoop' that
isn't in the business of making and testing their parts as this is no more
than rumor and hearsay. You take that kind of info just with a 'grain of salt'.
If you put all of the opinions and hearsay into a paper sack it is worth exactly
the price of the paper sack. Verify for your particular need!