Home Forums Hunting & Shooting AR and Tactical Rifles 223 vs 556 and guns

Ok so I have a mini 14 and a couple ar 15
My ar barrels are marked 556
I have reloaded a lot of ammo using small base dies
Will these shoot out of both?
My factory ammo is a mix of 223 and 556
Thanks
Just never really gave it any thought til now

This can be a can of worms…

You can shoot 223 marked factory ammo in a 5.56 all day long. You should NOT put factory 5.56 ammo in a rifle chambered in 223. The 5.56 ammo has a higher operating pressure and the 5.56 chamber has longer throat that may cause pressure spikes in a 223. A 223 Wylde can should either.

You didn't say what your Ruger is chambered in? If it's 556 then like himmelrr said no worries shooting either.

Often times, it's best to consult the manufacture. Some rifles are stamped ".223 rem", while they can still shoot 5.56 ammo. Never assume that is the case though. I have 3 barrels right now that are stamped for .223 rem, and they will also shoot 5.56 according to the factory.

This according to the manufacture:
Your Varmint Exterminator is safe with decent factory loaded 5.56 NATO ammo. We put .223 on the barrel as that is what is recommended for best results, match grade .223 ammunition.

They also go on to explain the difference between the 2:
The basic difference is that 5.56 NATO ammo tends to be hotter than .223 Remington. The leade dimension (freebore before the start of rifling) is longer on a 5.56 chamber, on a .223 chamber it is tighter. Therefore the .223 chamber can develop excessive pressure when a 5.56 NATO round is fired in it. Our chambers are all safe to fire 5.56 NATO or .223 Remington ammunition in.

IIRC all .223 chambered Ruger mini 14/Ranch rifles will also accept 5.56 except for the target models that had the adjustable barrel weight. At least, that has been repeated enough online and (I believe) in Ruger manuals to be treated as true.

Bill Ruger always said that his mini14s could be fired with either ammunition and said not to worry about anything

That’s my recollection also. That the Ruger Mini 14 barrels are stamped .223 but are actually 5.56 chambers. I would guess that it was Bill Ruger wanting to appear more PC. I remember reading that Ruger had hopes at one time that the Mini 14 would be adopted by the military and it was a popular prison guard rifle so it would make sense that it would have 5.56 chamber dimensions.

In reality though I’d have zero issue shooting 5.56 out of a .223 chambered rifle.

And with so many differing custom chambers in 223 you can run into same pressure issues with a load for your "223" thats unsafe in another 223 with a differing chamber..

Shoot 223 all the time as to factory ammo to be safe. But I've only run into pressure once in any of the guns. An AR15 of some type. Maybe an old SGW gun. Running IMI ball 5.56. That was hot ammo from the Israelis. But it never created an issue other than it was hot and left ejector marks.

remember "The A-Team" always used full auto mini-14's, shot alot, never hit nobody in 4 seasons of weekly shows!

When was growing up, .223 Remington and 5.56mm were the SAME DAMN THING.

The "differences" are pretty contrived.

The "NATO" cartridge DID NOT EXIST until 1983 or something like that. They wanted a heavier bullet but wanted it to go just as fast as the previous 5.56mm/.223 bullet (which is NOT NATO), or as close to it as possible. Well, automatically, that means higher pressure. So, naturally, the spec for 5.56mm NATO is a little higher than it was for 5.56mm/.223 Remington. The chambers are the same. If you bought a Colt AR15 or a Mini-14 in 1975 marked ".223", it is the same chamber as one today marked "5.56mm NATO", which is why they are all perfectly fine to fire with NATO ammunition..... and they were made way before NATO ammunition even existed.

The very minor chamber/throat dimensions I am figuring came from manufacturers of bolt action rifles chambered in .223. Bolt action .223 shooters generally are not the least bit interested in shooting cheap surplus ammo... and especially not green tip NATO ammo. 55 grain bullets are probably the heaviest they would ever use in the gun, and more likely to be shooting 50 or 45 grain hollowpoints. Rifling leads were adjusted to the lighter bullets and viola! You have ".223 only" chambers. That's my theory, anyway, but the ".223 only" chambers had to come from somewhere, and that seems logical.

The only Mini-14 that has this silly ".223 only" chamber is the aforementioned "target" version with the harmonic balancer on the muzzle. The whole thing was a gimmick.

And yes if small base, which has never been required in any 223/5/56 I"ve owned, it will fit all the chambers likely.

But bullet ogive shape and seating depth could, but likely won't come into play.

As can the load itself. Lets just go extremes. If you loaded absolute max in a long throated chambered 5.56 that load could be higher pressure in a really tight chambered short throat match 223 chamber.

A LOT of that is going to simply be case capacity and the other is going to be how far the bullet may be soft seated or jammed into the rifling.

an example is same cases and bullets in the same gun. Some for long range slow fire and some for mag length rapid fire.

75 amax. Yep I have bullets from way back. When you buy em 5000 at a time it happens LOL. Had to back down the powder charge maybe almost a full grain to retain same MV and pressure between a long seated like maybe 2.320 or longer? and a mag at 2.240. It decreases case capacity so its almost like shooting the same bullet in a 30-06 case and a 308 case if that makes sense.

Yep,

The A-Team was must see TV when I was in 1st grade and I had the lunchbox to prove it.

In a SAMI spec 223 rifle it isn’t going to damage anything. In a worst case scenario with a tight match chambered 223 shooting full pressure 5.56 with the bullet seated out as far as possible it’s going to be over pressure obviously and you would see indicators of it but I still can’t imagine anything catastrophic happening.

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That's right.
Who here knows of a catastrophic failure from firing 5.56 in a .223 chamber ?
This oft-frequented exercise is more theory than reality.

gosh this takes me back 20 years, i shot any and all milsurplus ammunition in the 3 mini 14s that I owned. never an issue.

Catastrophic no, but popped primers, yes. Ned Christianson makes a reamer that cuts the leade more than anything else to clean up 5.56 NATO chambers that from some companies turn out to be just loose 223 chambers. Losing a primer to must of us isn’t going to be anything other than an inconvenience if that primer winds up locking the trigger up. But for some it could be more serious.

Savage will just give you the lawyer-driven corporate line, "Just what's marked on the barrel". Wouldn't be surprised if that is the position of other companies as well.

Probably all of the owners manuals also say Factory only. NO reloads

The problem is when you start creeping up around higher pressures its only one more shot before a failure.

Ever see lugs sheared off an AR bolt? We have no clue why but I've seen it twice. The loads being run were not mild. Who knows if it was a flaw or length of exposure.

Doesn't mean I wouldn't do it. IE shoot 5.56 in 223 and that I might keep on.

But it also doesn't mean that the next might not be a wild ride when you pull the trigger

As to a harmonic balancer noted above, they work. Thats proven many times over.