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opaww 07-18-2008 10:52 AM

.223/5.56 Nato
I have a small question myself in regards to a .223 vs. 5.56 NATO. Some people say that shooting 5.56 NATO out of a bolt-action rifle like the Rem. 700 chambered in .223 is not a good idea sense the 5.56 NATO is slightly more powerful then itís civilian counter part the .223. Then I have also heard that it is ok to shoot either .223 or 5.56 from a good bolt-action rifle and it will not hurt anything.

My youngest son and I would like to get a good bolt-action rifle chambered in .223 but we would like to be able to fire Mil. Surplus 5.56 without worrying that we me damage the rifle.

We were thinking about the Rem. 700 in .223. Can this rifle handle the 5.56 NATO without any problems?

jeepcreep927 07-18-2008 11:06 AM

The NATO chamber 5.56 mm is rated at a higher pressure than SAAMI .223 chamber. I think the 5.56 is 60,000 cup? Anyhow that is one issue with firing 5.56 ammo in a .223 chamber. The freebore diameter, leade and throat angle are also dimensionally different which all lead to increased chamber pressure. I doubt a single 5.56 round would explode a .223 chambered action, maybe not even 50 rounds, but bottom line is the chambers are different so why risk it. .223 can however be fire from the 5.56 mm chamber with no risk to the firearm but accuracy will likely suffer a bit.

opaww 07-18-2008 11:14 AM

Thanks, I kind of thought along this line myself but was unsure sense there are people saying deferent things about it.

jeepcreep927 07-18-2008 11:21 AM

I have seen a lot of people say it's not a big deal, but again, the chambers are different so I wouldn't trust their "opinions" on doing it. I guess when I was a kid my dad and grandfather had absolutely ZERO tolerance for not following rules when it came to guns. One of those rules was only firing ammunition that the gun is marked for. Seems some people don't agree. On another forum I like there is a pretty lengthy discussion about guys firing .17hm2 in a .22lr. Sure you can, but why? Just to see what will happen? Some people...
Anyhow, if you get the 700 you might take it to a decent gunsmith and have the chamber reamed to 5.56 or .223 wylde which will fire both 5.56 and .223 interchangeably. Since the chamber dimensions are so close it probably won't cost much. Dillinger could probably shed more light on that though.

G21.45 07-18-2008 01:24 PM


Originally Posted by opaww (Post 32339)
.... My youngest son and I would like to get a good bolt-action rifle chambered in .223 but we would like to be able to fire Mil. Surplus 5.56 without worrying that we me damage the rifle.

We were thinking about the Rem. 700 in .223. Can this rifle handle the 5.56 NATO without any problems?

:eek: Nope, you shouldn't do that!

Winchester Bulletin

Paul Nowak
.223 Rem VS 5.56mm

There are a lot of questions about these two cartridges. Many people think they are identical - merely different designations for commercial and military. The truth is that, although somewhat similar, they are not the same and you should know the differences before buying either cartridge.

•The cartridge casings for both calibers have basically the same length and exterior dimensions.

•The 5.56 round, loaded to Military Specification, typically has higher velocity and chamber pressure than the .223 Rem.

•The 5.56 cartridge case may have thicker walls, and a thicker head, for extra strength. This better contains the higher chamber pressure. However, a thicker case reduces powder capacity, which is of concern to the reloader.

•The 5.56mm and .223 Rem chambers are nearly identical. The difference is in the "Leade". Leade is defined as the portion of the barrel directly in front of the chamber where the rifling has been conically removed to allow room for the seated bullet. It is also more commonly known as the throat. Leade in a .223 Rem chamber is usually .085". In a 5.56mm chamber the leade is typically .162", or almost twice as much as in the 223 Rem chamber.

•You can fire .223 Rem cartridges in 5.56mm chambers with this longer leade, but you will generally have a slight loss in accuracy and velocity over firing the .223 round in the chamber with the shorter leade it was designed for.

•Problems may occur when firing the higher-pressure 5.56mm cartridge in a .223 chamber with its much shorter leade. It is generally known that shortening the leade can dramatically increase chamber pressure. In some cases, this higher pressure could result in primer pocket gas leaks, blown cartridge case heads and gun functioning issues.

•The 5.56mm military cartridge fired in a .223 Rem chamber is considered by SAAMI (Small Arm and Ammunition Manufacturers Institute) to be an unsafe ammunition combination.

Before buying either of these two types of ammunition, always check your gun to find what caliber it is chambered for, then buy the appropriate ammunition. Most 5.56mm rounds made have full metal jacket bullets. Performance bullets - soft points, hollow points, Ballistic Silvertips, etc. - are loaded in .223 Rem cartridges.

Firing a .223 Rem cartridge in a 5.56mm-chambered gun is safe and merely gives you slightly reduced velocity and accuracy.

However we do not recommend, nor does SAAMI recommend, firing a 5.56mm cartridge in a gun chambered for the .223 Rem as the shorter leade can cause pressure-related problems.

Winchester Law Enforcement Ammunition
East Alton Illinois

alsaqr 07-19-2008 02:13 AM


I think the 5.56 is 60,000 cup?
You would be wrong. The US military uses psi. M193 ball ammunition generates 52,000 psi average pressure plus three standard deviations, not to exceed 58,000 psi max. PSI does not translate to CUP.

The US army measures pressure at the mouth of the cartridge. SAAMI measures pressure at the case body.

My favorite gunsmith tells me that he has measured casts from the chambers of nearly every new .223 rifle and that almost no one uses the original SAAMI chamber.

BTW: There are at least a dozen different 5.56mm and .223 chambers.

G21.45 07-19-2008 09:09 AM

This might shed a little more light on the subject -

And, here's more useful information. (Open the article's source links if you really want to get into researching this.)

NOTE: CUP and PSI can, indeed, be confusing! ;)

opaww 07-19-2008 10:28 AM

There is real good information here, and I thank you all for giving it. I believed along the lines of not using the 5.56 NATO ammo in a bolt action chambered for the .223. I had to ask to be sure sense I cannot get much in the way of reliable information locally here.

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