Firing 5.56 out of an M&P15I

Wally said:
am I the only one who thinks that spelling and grammar mistakes in a reply discredit the author? It's hard to take someone seriously when they can't handle the simple task of manipulating the english language.
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No arguments here! By the way, you forgot to capitalise the 'e' in English. ;)

I'm rather skeptical of the claim that 5.56mm ammunition is unsafe with a .223 chamber. I'm sure lots of 5.56 has been fired out of rifles with .223 chambers with nary a kaboom. I suppose there is a remote chance of unsafe pressure in a minimum dimension chamber, but a rifle like that would most likely be used with handloads, anyway.

It would be interesting to see the results of pressure testing with this combination. I'm sure that 5.56 ammo would give higher pressure than .223, but I doubt that it would be high enough to be dangerous.
 
Wally said:
am I the only one who thinks that spelling and grammar mistakes in a reply discredit the author? It's hard to take someone seriously when they can't handle the simple task of manipulating the english language.
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Wally, if you are going to criticize other people's English, you'd better get it right yourself, you made two mistakes.

In addition to capitalizing 'english' we also start sentences with a capital letter... now go play nice or you'll miss recess.
 
Just call Smith and ask. My mini 14 is marked 223 but Ruger will tell you the make it too 5.56 ammo but stamp 223 for the consumer market, I also have herd that Tavor is also like marked.
 
robertf said:
Wally, if you are going to criticize other people's English, you'd better get it right yourself, you made two mistakes.

In addition to capitalizing 'english' we also start sentences with a capital letter... now go play nice or you'll miss recess.
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Crap... beat me to it!
 
Difference

I am very interested to see what the consensus is on this issue, I have an ar and a 700P one marked 5.56 and one marked .223. I know that the dimensions are the same but have heard the same thing. Don't fire a 5.56 in a .223 or your d*ck will fall off. So what is the answer?
 
The only difference between 223 REM and 5.56 NATO is case neck length, the 5.56 neck being 0.014" longer. As far as pressure, the case dimensions are the same however Mil Ammo is typically heavier due to the application and would theoritically have less case capacity for powder. Standard Mil loads are 55 Grain FMJ at 3100 FPS I belive, which is well within SAAMI presure limits for 223 REM.
 
twig_40 said:
I am very interested to see what the consensus is on this issue, I have an ar and a 700P one marked 5.56 and one marked .223. I know that the dimensions are the same but have heard the same thing. Don't fire a 5.56 in a .223 or your d*ck will fall off. So what is the answer?
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Technically, it is not a good idea to shoot 5.56 out of a 223 chamber because of the throat and pressure differences. 223 will hit around 55,000 PSI and is proof tested to that pressure.

5.56 is specified at 62,000 PSI. Not that much higher but the chambers have to be proof tested up to 78,000 PSI to allow for manufacturing differences in bullets. So there's probably 5.56 NATO ammo floating out there that probably exceeds the NATO specification.



In terms of practicality, chances are no your gun will NOT explode and send shrapnel into your face. If anything what you will see first is signs of overpressure in the ejected brass, and probably should stop using the remaining rounds.

Now if we're talking a really tight match grade .223 chamber firing cheap 5.56 surplus ammo that has a bullet that's been improperly seated you're probably in a bit more trouble. But then why are you firing 5.56 cheap #### out of a match grade 223 chamber in the first place? :D
 
To reiterate - I am not asking about interchanging .223 for 5.56 in general. I am only asking about firing 5.56 out of a Smith & Wesson M&P15I which is marked 223 REM.

Carry on.
 
Truth be told I have launched hundreds of rounds of 556 out of my Rem 700P (223) and hundreds more of 762 (nato) out of my other 700P (308) that and a myriad of rifles marked 223 and vice versa with nary a problem......

The variances are so 'minute' that I would not worry, its pretty much like 87 octane gas from Chevron and 87 octane from Esso

In the end it is obviously up to you............
 
I always stick with whats marked on the barrel just for my own ease. Most Mfgr's mark their barrels properly. 5.56 and 223 may only be slightly different; but they are different none the less.
 
Im going shooting tommorow with fellow cgn 'thejudge', If you guys read in the Province Paper Saturday morning that a guy was flown by air ambulance to 'Royal Columbian Hospital' with injuries to his face and extremities ( arms/fingers ) you will realise that karma bit me in the ass..............;)
 
Wally said:
am I the only one who thinks that spelling and grammar mistakes in a reply discredit the author? It's hard to take someone seriously when they can't handle the simple task of manipulating the english language.
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I can only assume you are revering to my post. If so you can go f*ck yourself as English is NOT my first language.

If you are really concerned you can always phone S&W and ask if you can shoot 5.53 in you .223 marked barrel. As for backing up my previous post I can only say what I saw on one of the Brownell videos. What he said made sense to me. This is straight of Bushy's web site

All Bushmaster rifles are chambered to accept 5.56mm ammunition and always have been. The NATO Spec 5.56mm chambers have a longer "leade" or throat than the SAAMI Spec .223 caliber chambers which have about half of the leade or throat of the 5.56mm chambering. While it is safe to fire both 5.56mm and .223 caliber ammunition in our rifles, the 5.56mm ammunition should not be fired in rifles chambered in .223 caliber as they will develop very high pressures.
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I know you have a S&W bit it might be the same thing. Call/email them and ask. Or take it to a gunsmith and let him tell you.
 
It seems to me that you are not really gonna get a for sure answer on here as alot of people say its ok then some say its not ! If I were you I would just call Smith&Wesson and talk to one of thier people at least then you will get an answer from them not just someones opinion on here right ! Sorry I know there are people on here that do know things but well you know what I am sayin right!!
So here is my other opinion for you !!
If it says .223 , then shoot .223 !
 
It was too painful, I couldn't take it anymore... especially Wally, the remedial English teacher who got his teaching certificate from the new Chinese Wal-Mart. I just called S&W and they said the M&P-15I is "strictly .223." Probably just for legal reasons but nevertheless.
 
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