.223 and 5.56?

[PILMAN]

I've been told not to use 5.56 in a .223 gun because there was too much pressure and could cause the gun to explode? I'm in the process of getting a gun built and my receivers .223 (the only one they make), barrels 5.56 and the bolt is 5.56. I've been told that I can use .223 in a 5.56 however without a problem, anyone able to confirm this? I thought it was the same round esentially?

 

[GardDog223]

See this thread:


http://www.thehighroad.org/showthread.php?t=262961&highlight=223+5.56

 

[TexasRifleman]

As long as your barrel is chambered for 5.56 you are good with both.

They are NOT identical but they are pretty close.

If you have a .223 chamber you should not use 5.56 ammo.

You want the long version just yell.

 

[cheygriz]

Basically, the dimensions are identical. the 5.56X45 is loaded to slightly higher pressure, and there is approx. .020 inch of "freebore" in a military chamber to compensate for this. Since the barrel is the part where the chamber is cut, you can use a .223 action, and just have the barrel chambered for 5.56X45. No problem. And yes, you can use commercial .223 in the military chamber. It isn't loaded quite as hot. Although, in reality, the difference is pretty small.

 

[Smellvin]

Here's your source for approximately 1295.76% more information than you ever wanted about 5.56 NATO and .223 ammo (it agrees that a barrel labeled 5.56 should be able to fire both while the inverse isn't necessarily true).

http://www.ammo-oracle.com/body.htm

 

[Bartholomew Roberts]

Also I doubt you would cause the rifle to explode absent some other problem, a more likely scenario is you would just get a stuck case/bolt. Check the Rifle forum for a discussion of someone shooting 5.56mm through their .223 Kimber bolt-action for an example.

 

[TX1911fan]

My Rock River AR has a Wilde chamber that allows it to shoot both, so I would guess either RRA is using this as a marketing gimmick, or there is a reason to have a special chamber that will allow it to shoot both.

 

[akodo]

here's the scoop as I understand it.

5.56 is for semi-autos. These feed and cycle a bit better with slightly hotter loads, but also, the bullet flys free a tiny bit before entering the barrel, akin to a revolver barrel/cylinder gap. This means accuracy is slightly less good that what it could be.

.223 is the same ammo but tweaked for bolt action and single shot rifles, where accuracy is going to be more important, and as you hand cycle, gas for cylcing is of course not a concern. Also, these are sporting arms not war arms so rejacking a round and fiddling around aren't going to cost you your life, just maybe your trophy game animal. Anyways, because of these different concerns (accuracy vs reliabilty in a semi-auto) the bullet in a .223 chamber does NOT travel as far before entering the barrel. It's got less room. So if it was loaded the same as the 5.56 (designed for the more spacious chamber) in the 'cramped quarters' it would build up more pressure than intended. So they slightly downloaded the .223 to more meet the requirements of a boltaction rifle.

However, most boltactions you can get in .223 are also available in .220 swift, .22-250, etc, which work at higher pressures, so really you should be fine firing 5.56 in a quality boltgun.

For any semiauto, even if it says .223, it is probably designed with that extra spacious 'jump' for reliabity. The only exception to this are going to be certain heavy barreled varmint style semiautos tuned for the greatest accuracy.

 

[sansone]

I fired many 5.56 in my mini-14. sometimes the bolt would be stuck shut on a live round. in otherwords, if the bolt closed on a live round, and for some reason I wanted to manually extract the live round , the bolt and case would be dificult to extract/retract. if fired, the gun would cycle and feed rounds normally. I believe the rifle chamber/throat area was jamming or crimping the caseneck/bullet area of the 5.56 military round. decided to take them all apart, resize & trim all the cases(they needed much trimming off the caseneck) & put them back together again. now they operate flawlessly

 

[JesseL]

My Rock River AR has a Wilde chamber that allows it to shoot both, so I would guess either RRA is using this as a marketing gimmick, or there is a reason to have a special chamber that will allow it to shoot both.

My understanding it that while a 5.56 chamber will handle .223 just fine from a safety standpoint, the larger chamber dimensions will compromise accuracy.

The Wylde chamber is supposed to be a dimensional compromise that is able to handle both .223 and 5.56 while maintaining a higher degree of accuracy than the standard 5.56 chamber.

 

[1911 guy]

Freebore.

The cases are identical. 5.56mm is loaded a bit on the warm side, the freebore prevents pressure spikes. .223 Remington requires less freebore because pressures are reduced. You're not likely to do much harm to a .223 rifle by shooting the odd 5.56 round, but if you have a problem and the manufacturer can trace it to ammo interchange, they might not warrant the work.

I had a .223 rifle as a kid that had a tightly cut chamber. Loading 5.56 rounds would always, as in every time, seat the bullet in the lands. Closing the bolt was very different depending on what was in the magazine. Didn't know any better at the time.

As far as the accuracy issue, handloading solves that. Seating to max mag length in an AR will eliminate some of that freebore. Work backward toward min OAL until you find the "sweet spot" for your rifle.

 

[Dustinthewind]

.223 and 2.56?

My friend brought this to my attention when he was building his AR. The Sierra rifle manual lists them as one and the same. I have just measured once fired 5.56 NATO brass from several manufactures and the case length varies from 1.750 to 1.765. Various once fired commercial brass all measure out to1.750, however these were all fired through my Mini-14 and all cycled fine, although the military ammo is noticibly hotter.