.223 vs 5.56?

[Rumpelhardt]

From what I gather from my limited reading the problems may start when you have a .223 chamber that has a throat that is at the shortest end of the accepted tolerances and 5.56 ammo that is at the longest.
Chambering the round when this condition exists is supposed to crimp the mouth of the case into the bullet so it can’t open properly to release the bullet significantly raising pressure possibly dangerously so.

[jmoore]

Chambering the round when this condition exists is supposed to crimp the mouth of the case into the bullet so it can’t open properly to release the bullet significantly raising pressure possibly dangerously so.

Not so much. It's just that the throat of the .223 Rem chamber is shorter, nominally. So the bullet may either have a shorter run to the rifling or engage it upon chambering. Both will raise pressures.

Folk can't see electrons either, but they dont fret over them nearly as much. I think electrons are much more dangerous than the 5.56vs.233 thing! Watch out, your screen is glowing! So much energy flowing that the photons are all excited...

[Bob Womack]

However, there are manufacturers such as Olympic who build tight-chambered ARs and specifically warn against use of 5.56 ammo and state that use will void the warranty. Who wants to void the warranty?

Bob

[browningautorifle]

I've never had an AR with a warranty, they were either so old or a parts gun and had none. I did however have several Oly Frankenguns and never had problems with anything...matter of fact, the only AR thing I ever had problems with was a short barrel I assembled to a kit and it wouldn't work properly. Turned out the gas port was almost an 1/8" so it was somewhat over gassed.

[jmoore]

However, there are manufacturers such as Olympic who build tight-chambered ARs and specifically warn against use of 5.56 ammo and state that use will void the warranty. Who wants to void the warranty?

"Not I!", said the cat. But unless they plaster that info on the barrel, then I'd guess they aren't too concerned. The original buyer ought to know what they're getting (a bit of a stretch, but...), however, when it shows up on the used market there is a high likihood that some 5,56 will be used. Colt marked their rifles .223 for ages even though they weren't. So it's not unreasonable to think that folk won't pay much attention to a mere caliber marking on the side of a receiver at this late date. But I do understand that 100% blanket statememts rarely work. There's probably ARs out there with custom chambers that won't shoot ANY factory 5,56 or .223 ammo.

[DaveN]

Thank you. Originally wrote wondering if it was two names for the same thing. Looking at them I couldn't tell the difference. The info has been very let's say conclusively inconclusive to say the least.
Mine has 5.56 on it so I'm good and I have no .223 bolt guns so I'm good twice over.
Sometimes it's nice to see a thread that you thought was dead come back to life... Makes me think I can ask a meaningful question now and then.
Thanks again!!

[browningautorifle]

I still don't think it matters.

[langss]

Initially I never actually kept track of what I shot out of which AR because it was so inexpensive I never considered reloading for it. Then I got a Winchester chambered in .223 to use the brass from the AR's in. I never paid attention to whether it was 5.56 or .223 I was shooting out of it, and never noticed any signs of over pressure or anything else, that is until I bought the Remington XP 100 in .223. The first shot told me something was wrong when I had to open the bolt with a block of wood. Obvious sign of over pressure. But me being me I thought it was perhaps just the brand of ammo and pressed on with a different brand with the same result. So I tried another brand and had no sign of over pressure. I now know what I did and I will say that Remington builds a pretty tough gun to withstand what amounts to serious over pressure loads and still shoot just fine.The point being that if it says 5.56 on your barrel your good to use either. If it says .223 on your barrel....stick with .223 or carry a block of wood to open your bolt.

[jmoore]

...Remington XP 100 in .223. The first shot told me something was wrong when I had to open the bolt with a block of wood. Obvious sign of over pressure. But me being me I thought it was perhaps just the brand of ammo and pressed on with a different brand with the same result. So I tried another brand and had no sign of over pressure. I now know what I did and I will say that Remington builds a pretty tough gun to withstand what amounts to serious over pressure loads and still shoot just fine.The point being that if it says 5.56 on your barrel your good to use either. If it says .223 on your barrel....stick with .223 or carry a block of wood to open your bolt.

The wood block works up to a point. But I've seen more than one 700 bolt minus it's handle after the braze fails! One was in fact a .223. But in that case it was the owner's fault for getting too aggresssive with his loads. Blew the entire case head off BEFORE he proceded to further mangle the bolt. Funnily enough, the rifle was later returned to service with the same bolt after some major rework including the addition of a SAKO type extractor and a silver soldered ring replacing the ruined area surrounding the bolt face...

[browningautorifle]

Blew the entire case head off

But that was the reloader's fault. I still maintain no problem.