What is the actual chamber on a S&W MP-15 .223/5.56?

akmtnman99669

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I can not seem to get a strait answer. Is this a .223 or a 5.56? I know you can shoot a .223 load out of your 5.56, but can have pressure problems shooting a 5.56 out of your .223. So is a S&W M&P-15 Sport a .223 or a 5.56?
 
You can also get pressure signs from a 223 in a 5.56...

They're the same case dimensions. The difference is how any one round is set-up. IE: Bullet, charge, OAL, etc. ALL of this needs to be considered when looking at a load to shoot in your rifle.

The 223 Rem and 5.56X45 NATO are the same round. 5.56 marked chambers are typically set-up to shoot the longer steel-core FMJ military rounds, so they have a touch longer leade. If you have a short cut 223 chamber and stick a long 5.56 load into the lands, you could see pressure. But, fundamentally, they’re the same.

The only way to answer this is you need to shoot your intended load and evaluate for signs of high pressures. There is no universal 223/5.56 chamber dimension, literally dozens of different reamer specs exist.

IIRc, the S&W is set-up with a touch longer leade to accommodate any and all factory loads. But only shooting and evaluating the brass and such will be definitive.
 
M&P Sports will have a 5.56 chamber.

I know of 0 big AR15 manufacturers that chamber a rifle in anything other than 223 Wylde or 5.56.

The liability is too great for them to chamber a rifle in straight 223 with the plethora of 5.56 on the market and many people not knowing the difference. Only custom builders would be building anything other than 223 Wylde or 5.56.
 
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While I can't find the exact article I read, I remember it stated that the .223/5.56 have different INTERIOR case dimensions due to the case walls being thicker in 5.56 to allow for higher pressures. Therefore the 5.56 chambers were ?stronger? and would thus allow the .223 with thinner walls and less pressures to be used but not vice-versa, (5.56 in .223 chamber).

Anywhooo, that's all I have on that.
 
wow, we went a record amount of time since the last time this came up!

i read it on the internet, it must be true!
 
Originally Posted By: HereticWhile I can't find the exact article I read, I remember it stated that the .223/5.56 have different INTERIOR case dimensions due to the case walls being thicker in 5.56 to allow for higher pressures. Therefore the 5.56 chambers were ?stronger? and would thus allow the .223 with thinner walls and less pressures to be used but not vice-versa, (5.56 in .223 chamber).

Anywhooo, that's all I have on that.


He asked if it was a 223 or 556 not can he shoot 223 or 556 in it
 
Originally Posted By: JoeBobOutfittersM&P Sports will have a 5.56 chamber.

I know of 0 big AR15 manufacturers that chamber a rifle in anything other than 223 Wylde or 5.56.

The liability is too great for them to chamber a rifle in straight 223 with the plethora of 5.56 on the market and many people not knowing the difference. Only custom builders would be building anything other than 223 Wylde or 5.56.

Colt makes one in 223 its called the 6900
 
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Originally Posted By: bryan hOriginally Posted By: HereticWhile I can't find the exact article I read, I remember it stated that the .223/5.56 have different INTERIOR case dimensions due to the case walls being thicker in 5.56 to allow for higher pressures. Therefore the 5.56 chambers were ?stronger? and would thus allow the .223 with thinner walls and less pressures to be used but not vice-versa, (5.56 in .223 chamber).

Anywhooo, that's all I have on that.


He asked if it was a 223 or 556 not can he shoot 223 or 556 in it


semantics
 
Originally Posted By: 6724Originally Posted By: bryan hOriginally Posted By: HereticWhile I can't find the exact article I read, I remember it stated that the .223/5.56 have different INTERIOR case dimensions due to the case walls being thicker in 5.56 to allow for higher pressures. Therefore the 5.56 chambers were ?stronger? and would thus allow the .223 with thinner walls and less pressures to be used but not vice-versa, (5.56 in .223 chamber).

Anywhooo, that's all I have on that.


He asked if it was a 223 or 556 not can he shoot 223 or 556 in it


semantics

It was a question if the GUN he has was a 223 or 556 . It was not about logic...
 
Originally Posted By: bryan hOriginally Posted By: 6724Originally Posted By: bryan hOriginally Posted By: Heretic

He asked if it was a 223 or 556 not can he shoot 223 or 556 in it
semantics

It was a question if the GUN he has was a 223 or 556 . It was not about logic...

Originally Posted By: akmtnman99669I can not seem to get a strait answer. Is this a .223 or a 5.56? I know you can shoot a .223 load out of your 5.56, but can have pressure problems shooting a 5.56 out of your .223. So is a S&W M&P-15 Sport a .223 or a 5.56?

He was most definitely insinuating that you cannot/should not shoot 556 in 223 barrels.
 
Originally Posted By: akmtnman99669I can not seem to get a strait answer. Is this a .223 or a 5.56? I know you can shoot a .223 load out of your 5.56, but can have pressure problems shooting a 5.56 out of your .223. So is a S&W M&P-15 Sport a .223 or a 5.56?

Everyone is trying to be Dr Phil here so please enlighten us on what you wanted to know thanks.........
 
Originally Posted By: bryan hOriginally Posted By: 6724Originally Posted By: bryan hOriginally Posted By: HereticWhile I can't find the exact article I read, I remember it stated that the .223/5.56 have different INTERIOR case dimensions due to the case walls being thicker in 5.56 to allow for higher pressures. Therefore the 5.56 chambers were ?stronger? and would thus allow the .223 with thinner walls and less pressures to be used but not vice-versa, (5.56 in .223 chamber).

Anywhooo, that's all I have on that.


He asked if it was a 223 or 556 not can he shoot 223 or 556 in it


semantics

It was a question if the GUN he has was a 223 or 556 . It was not about logic...

did i miss something?

the original question was what the chamber is in an M&P15, BUT the subsequent posts are not. the subsequent posts refer to the old wives tale concerning 223 vs 5.56.

Definition of semantics (n)
Bing Dictionary

se·man·tics
[ sə mántiks ]

study of meaning in language: the study of how meaning in language is created by the use and interrelationships of words, phrases, and sentences
 
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Thanks for all the input. Where I live it is hard to put your hands on a rifle. Most of the firearms bought around here are used, or bought on the internet. So I wanted to ask around to see if anyone knew for sure if it was a .223 or 5.56. If it was a .223 I would have looked at other brands to find a 5.56.
 
Originally Posted By: akmtnman99669Thanks for all the input. Where I live it is hard to put your hands on a rifle. Most of the firearms bought around here are used, or bought on the internet. So I wanted to ask around to see if anyone knew for sure if it was a .223 or 5.56. If it was a .223 I would have looked at other brands to find a 5.56.


THANKS
 
Originally Posted By: Widow maker 223DPMS chambers in .223 rem. But thats irrelivent. Shoot away

My DPMS upper barrel is stamped 5,56mm.
 
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