5.56 verse 223 question

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taozen79

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I have a ar15 A1 , I believe, colt upper , barrel marked
C MP C

can it shoot 5.56??????

THANKS for any help

Buddy
 
markings

BARREL:
DIAMETER:
0.625" at the Front Sight Base
LENGTH:
20"
TWIST RATE:
1/12
MARKINGS:
C CM C
 
As it was explained to me by folks I trust:

If chambered for 5.56 - can shoot either 5.56 or .223

If chambered for .223 - can only safely shoot .223 (headspace & pressure differences)

What's stamped on the gun, 5.56 or .223?
 
Headspace is the same, leade is longer in the 5.56.

Pretty sure Colt chambers all their guns 5.56.
 
BARREL:
DIAMETER:
0.625" at the Front Sight Base
LENGTH:
20"
TWIST RATE:
1/12
MARKINGS:
C CM C

this barrel is older than the ones marked 5.56. it is an sp1
By 1969 and before serial number 1,750,XXX Colt's chrome chamber barrels were marked C MP C, and the proof markings and C were moved to the same spot. This marking was used as late as 1970 or 1971 and serial number 4,552,XXX. The C means Colt’s, the M means Magnetic particle inspected, the P for Proof fired, and the C near the muzzle for Chrome chamber. (late C MP C pic provided by yfs200):
 
BARREL:
DIAMETER:
0.625" at the Front Sight Base
LENGTH:
20"
TWIST RATE:
1/12
MARKINGS:
C CM C
this is the barrel markings....from the colt sp1
 
I have a AR bought in 1978.It has had a lot of 5.56 put through it and never failed to function and stays accurate. Byron
 
#32


223 vs. 5.56 (and .308 vs. 7.62x51).

32. There is essentially no difference between commercial .223 and military 5.56 ammo. The same is true with .308 and 7.62 ammo. The military stuff has slightly thicker brass with a tiny bit more length in the shoulder and I hear this is for strength when feeding through full-auto guns that tend to slam the rounds into the chamber violently. But otherwise, there doesn’t appear to be any difference that I have noted after many years of shooting both military and commercial ammo through my .223 and .308 rifles, both bolt action and semi-auto although with some guns with tight chambers closing the bolt on military ammo can be a bit snug. It is a popular misconception that military 5.56 ammo is loaded to higher pressures than commercial .223 but it is not.
 
32. There is essentially no difference between commercial .223 and military 5.56 ammo. The same is true with .308 and 7.62 ammo. The military stuff has slightly thicker brass with a tiny bit more length in the shoulder and I hear this is for strength when feeding through full-auto guns that tend to slam the rounds into the chamber violently. But otherwise, there doesn’t appear to be any difference that I have noted after many years of shooting both military and commercial ammo through my .223 and .308 rifles, both bolt action and semi-auto although with some guns with tight chambers closing the bolt on military ammo can be a bit snug. It is a popular misconception that military 5.56 ammo is loaded to higher pressures than commercial .223 but it is not.

Good explanation. Too bad SAAMI doesn't agree with you. BSW

From: http://www.saami.org/Unsafe_Combinations.cfm

In Firearms Chambered For---Do Not Use These Cartridges
223 Remington--------------5.56mm Military
 
taozen79 0842 CST said:
5.56 verse 223 question
I have a ar15 A1 , I believe, colt upper , barrel marked
C MP C

can it shoot 5.56??????

THANKS for any help

Buddy
taozen79 0916 CST said:
HELP 'bumped"
HELP

If I might point out that it doesn't make sense to expect a fast response when you post during the work day.

Also, "bumping" the thread after a half hour without a response isn't going to send out psychic waves to get everyone to immediately run to their keyboards to answer you.

Please don't do this any more.
 
It is a popular misconception that military 5.56 ammo is loaded to higher pressures than commercial .223 but it is not.

it's popular because, iirc, the 5.56nato max avg pressure number is a good bit higher than the .223rem ....buuuuuut... units matter and one is in CUP and the other in PSI, so good luck comparing
 
Search is your friend--

.223 is safe in 5.56 chambers, not always the other way around...

Some mfgs are marked .223, but 5.56 is ok--ie Mini 14s...

Always go by the MFG recommendation...
 
There is around 12,000 psi more to a 5.56 over .223. Call colt, ask them, Im sure they will tell you that the chamber is 5.56X45mm.
 
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