Stupid question of the week: is M855 safe in ARs?


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1KPerDay
November 11, 2009, 12:40 PM
http://www.inetres.com/gp/military/infantry/rifle/556mm_ammo.html

According to this, M193 chamber pressure is 52,000 psi, and m855 is 55,000. I assume any quality AR can handle the pressure.

They also say:
This ammunition should not be used in the M16A1 except under emergency conditions, and only at targets less than 90 meters in distance. (The twist of the M16A1 rifling is not sufficient to stabilize the longer projectile of the round).


I assume a Colt SP1 has the slower twist... and I shouldn't shoot m855 through mine?



STUPID QUESTION #2:

Cartridge, 5.56mm, Ball, M855, Lead Free

The M855 "lead free" ball cartridge has a bullet with a conical steel insert and a tungsten composite core in a copper alloy jacket. The intended use is to maintain environmentally "clean" ranges.

The cartridge is identified by a green bullet tip.

How do you tell the difference between the 2 types of M855 green tip? Cut one in half? :confused:

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Z-Michigan
November 11, 2009, 01:07 PM
You are not likely to encounter M855 lead free on the civilian market.

M855 is safe in any AR that has a 5.56mm NATO chamber rather than a .223 Remington chamber. Your AR should be marked but the markings can be wrong. Search on this topic, many threads.

M855 will stabilize if you have a 1:9 or faster twist barrel. In a slower twist barrel (1:10, 1:12, 1:14) it is safe to use, assuming a 5.56mm NATO chamber, but likely will not stabilize.

rcmodel
November 11, 2009, 01:11 PM
I assume any quality AR can handle the pressure.They were made for use in the M16, so it is safe to assume any AR-15 with a 5.56 NATO chamber is safe with them.

All Colt SP-1's had 1/12 rifling and will not stabilize the M855 very well, if at all.

I don't know how you tell the differance but cutting one in half should work.

rc

ny32182
November 11, 2009, 01:24 PM
The barrel marking will almost always be more definitive than a reciever marking regarding what kind of chamber and twist specs you have. (Obviously if it was a rifle assembled outside a factory, it is the only marking that matters at all.)

If it is marked 5.56, and with a twist of 1:9 or faster, I would not hesitate at all to shoot M855 spec ammo in it.

1KPerDay
November 11, 2009, 01:27 PM
Thanks guys. I assume SP1s have 5.56 chambers?

I won't shoot the m855 in it; just curious.

Z-Michigan
November 11, 2009, 01:29 PM
If it is marked 5.56, and with a twist of 1:9 or faster, I would not hesitate at all to shoot M855 spec ammo in it.

Generally agree but some manufacturers have been known to mark barrels as 5.56 when they actually have a .223 chamber. You'd have to do a search for details. I don't think Colt has been known to do such a thing but I'm not positive.

rcmodel
November 11, 2009, 02:03 PM
Colt SP-1's were all .5.56 NATO.

They never made an AR that wasn't except for the stainless steel barreled match guns in .223. They will be so marked on the lower barrel I think.

rc

kwelz
November 11, 2009, 03:05 PM
RC you are correct. But the SP-1 had to slow of a twist for the longer 855 bullet.

1KPerDay
November 11, 2009, 03:57 PM
Yeah, he noted that in his post above. Thanks all. :cool:

Maverick223
November 11, 2009, 05:13 PM
As others have mentioned, it is fine for any 5.56NATO rifle. It should shoot fine in any twist (with the possible exception of 1 in 14") as long as you don't use tracers (which are longer and require a faster twist to compensate). :)

rcmodel
November 11, 2009, 05:19 PM
I disagree.
M855 are both partial steel core & boat-tail, and are much longer then 60 grain flat base spitzers.

A 20" SP-1 rifle with 1/12 would be marginal at best with them.
A 16" SP-1 carbine with 1/12 probably would not stabilize them.

rc

cameron.personal
November 11, 2009, 05:25 PM
Absolutely DO NOT shoot the M855 through an AR15. This military ammo and will destroy your rifle.

Send it to me (PM for shipping address) and I will shoot it through my M4 and let you know how it was.

Cameron

RockyMtnTactical
November 11, 2009, 05:34 PM
Perfectly safe to use in your AR15, but depending on your twist rate, it may not shoot very accurately. As long as your twist rate is faster than 1/12 you shouldn't have any problems.

rcmodel
November 11, 2009, 05:36 PM
He has an SP-1 and they are all 1/12.

rc

RockyMtnTactical
November 11, 2009, 06:02 PM
Must've skimmed through to fast and missed the part where he said he had an SP1.

EddieNFL
November 11, 2009, 06:26 PM
Generally agree but some manufacturers have been known to mark barrels as 5.56 when they actually have a .223 chamber.

Armalite has in the past. Don't know if that's still the practice.

M1key
November 12, 2009, 03:38 PM
Some manufacturers mark .223 when it is in fact a Wylde chambering or 5.56. (liability issues). Rock River and Ruger Mini-14 use Wylde I believe. I have Bushmaster barrels marked .223. Don't remember the others...

rcmodel
November 12, 2009, 04:01 PM
Colt SP-1's were marked .223 on the lower receiver, but are in fact 5.56 NATO chambered. Ruger Mini-14's of the day were the same.

They were made back in the day before there was all the SAAMI fooforall about the difference.

Back then, there was only the M193 55 grain FMJ-BT GI load, and they were perfectly safe in either chamber.

The only problem I ever heard of back then was some SAKO Vixen .223 Rem rifles that got made with .223" barrels instead of .224" barrels.
And some Remington 40X match rifles with very tight .223 match chambers & barrels.

They both would sometimes blow primers with GI ammo.

I am still of the openion that much has been made about nothing when it comes to normal .223 chambers and normal 5.56 ammo being dangerous.
It may be dangerous with the longer GI tracer ammo but I have never shot any of it in a .223 so don't know.

rc

benEzra
November 12, 2009, 04:05 PM
Rock River and Ruger Mini-14 use Wylde I believe.
I think currently, RRA offers true 5.56x45, .223, or Wylde (your choice), but 5.56 marked guns are true 5.56 chambers, as I understand it. Not sure what they've done in the past, though.

Maverick223
November 12, 2009, 04:28 PM
It may be dangerous with the longer GI tracer ammo but I have never shot any of it in a .223 so don't know.I don't believe that it poses any danger, only unlikely to stabilize due to the additional length.

:)

1KPerDay
November 12, 2009, 05:07 PM
I believe RC was talking about shooting 5.56 tracer (longer bullet) in a true .223 chamber.

the OCL is still the same, though, right? They just seat it deeper in the case IIRC.

Maverick223
November 12, 2009, 06:42 PM
I believe RC was talking about shooting 5.56 tracer (longer bullet) in a true .223 chamber.In that case it may be a concern, but I wouldn't think it would be any different from any other 5.56.

the OCL is still the same, though, right? They just seat it deeper in the case IIRC.Correct, it is still within OAL specs., so very little if any change in cartridge length.

:)

Avenger29
November 12, 2009, 06:55 PM
I think currently, RRA offers true 5.56x45, .223, or Wylde (your choice), but 5.56 marked guns are true 5.56 chambers, as I understand it. Not sure what they've done in the past, though.

I'll have to look into it, but just because it's stamped "5.56mm" on the bbl doesn't make it so.

I don't think it's so much of a "dangerous" condition as it is, however, a reliability issue.

RockyMtnTactical
November 12, 2009, 09:35 PM
RRA is indeed putting out 5.56 barrels, along with .223 Wylde for their match or varminters (I think all of the SS barrels).

armsmaster270
November 13, 2009, 12:36 AM
My Mini 14 is stamped 5.56/.223

MarineOne
November 13, 2009, 01:22 AM
My Bushmaster is stamped NATO 5.56 1/9. I've shot both 5.56 and .223 from it with no problems.


Kris

1 LT MPC
November 13, 2009, 04:40 PM
I've got a Colt AR 15A2 HBAR marked .223 on the receiver and 5.56 on the barrel. What's up with that? I never noticed it before but I purchased the rifle new around 1991. I assume it'll shoot both. My dad had it until he passed and it's never been fired.:confused:

rcmodel
November 13, 2009, 05:07 PM
Colt used to mark all their commercial AR-15 semi-auto receivers .223 to differentiate them from M-16 full-auto receivers marked 5.56.

And like I noted in my earlier post, back then there was not an SAAMI warning about the difference, as there wasn't much difference..

Later on there were also H-Bars made with stainless steel match barrels chambered in .223, as well as similar ones in 5.56.
Only the barrel marking told the tail of which one it was.

rc

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