mp 15i barrel marked .223 will it be safe to shoot 5.56

[icelink]

Just was wondering if it is safe to shoot 5.56 out of a smith And Wesson mp15i that is marked .223 on the barrel I've been reading mixed thoughts on other website's.....some say NO some say YES some say catastrophic failure.....some say it needs a break in period.....fire a few hundred .223 then it will be ready for 5.56 what do u gunnutz think?

 

[armycat]

SAAMI lists using 5.56mm in a .223 firearm as an unsafe firearm/ammunition combination. Many .223 have a shorter chamber leade which can cause unsafe chamber pressures if 5.56mm is used.

Google SAAMI, on the left side of the web page there is a publications tab, click on that, then informational brochures, the unsafe firearm/ammunition combination brochure will be there.

 

[icelink]

Sammi sais do not use 5.56 "military" but nothing about 5.56 is the norinco spam can stuff 5.56 military?

 

[barsik]

this has been a topic of contention for quite some time, my opinion is that it not a good idea. depending on the manufacture and spec, a round developed specifically for the long freebore of the 556 NATO rifle or carbine may hold a powder charge that will exceed SAAMI pressure limits in the shorter freebore of the commercial 223 rifle. it probably won't grenade the rifle, but it will be hard on it, kind of like running max + handloads.

 

[Waynetheman]

If it's marked 223 I'd stick with that. If marked 5.56 then use both. Whoever said 223 chamber will break-in into a 556 needs to wear a helmet.

But besides all that the only way to truly know is to measure it. Some 223 marked guns are only marked that way for export reasons and are otherwise the same.

 

[sky52]

^^ some manufactures also marked it as 223 and ream the chamber to either 556 for export or 223 wylde which is safe to shoot both

 

[Waynetheman]

Yep! That's what I meant to say that they are otherwise 556 chambers.

 

[tjhaile]

It is probably OK, but you need to be aware of potential risk. I would shoot a few rounds of whatever 5.56 you want to use and stop shooting it if you see any bad signs, like popped primers. Catastrophic failure is unlikely.

Some data can be found here:
http://www.luckygunner.com/labs/5-56-vs-223/

 

[Greenhorse six]

^^^ What he said , if the rifle is properly made it shouldn't be an issue running 5.56 in a .223 .

 

[Scamaniac]

There is a sticky at the top of this forum with the answers you seek.

 

[Kaberday]

I went through the same thing with my m&pi as well. I actually read on an American forum that the m&pi was actually chambered in 5.56 but stamped 223 for export purposes, how ever I did call s&w and was told to use only 223, so that's all I use. I do believe there is a way to confirm if the chamber is 5.56 or 223 but not sure how.

 

[sky52]

Headspace gauge would tell the story

 

[crashcollins]

^^^ What he said , if the rifle is properly made it shouldn't be an issue running 5.56 in a .223 .

Aside from accelerated wear and possible parts breakage! But ya a catastrophic failure is unlikely.

 

[Greenhorse six]

Aside from accelerated wear and possible parts breakage! But ya a catastrophic failure is unlikely.

What accelerated wear? if the rifle is properly built this shouldn't be an issue , this is a rifle that was designed for military ammo use from the get go , and as far as parts breakage , that'll happen with .223 just as easy as 5.56 , if it's going to happen.

 

[Dietz]

Pretty damn sure the .223 markings are just for export purposes.

I don't think S&W makes a dedicated .223 AR.

 

[tjhaile]

Headspace gauge would tell the story

The major difference is all in the throat dimensions. Michiguns does sell a gauge that will determine whether a chamber is .223 or 5.56, but is not a headspace gauge. It will drop freely into a 5.56 chamber and stick slightly in a .223 chamber.