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Posted: 9/4/2012 7:40:08 PM EDT
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Ok guys, pardon the newbe question here. I've been around the board for while, but have only recently gotten into the black rifles.
I had a friend that had an AR and got into some money trouble and I bought it off him to help out. It's a M4gery on a bushmaster lower. The lower has the .223-5.56 markings on it. The ONLY markings I can find on the barrel are in front of the front sight, and are "M1S" and "1-9" I know that the "1-9" refers to twist and should handle up to 75gr in I remember right (but I've been wrong, many,many times  ) and I also have learned that the M1S a "Model 1 Sales" barrel. This leads me to think that it's at least not the upper that came on the came on the gun.
Here is the rub, how can I tell what the chamber is made for .223 or 5.56? The gun shoots good and I really like it, so it's not a huge deal, I've just got a line on some 5.56 ammo that I'd like to take advantage of. UPDATE: I just got off the phone with their customer service dept. They informed me that unless it was MARKED. 223, then it was 5.56. They were very helpful and answered all my questions. So they get a big atta-boy for that. Matt Thanks for your time guys, I know that y'all will set me on the way of the black rifle 
Matt |
| Not looking at it, but I'm pretty certain my Model 1 says 5.56 in the immediate vicinity of the M1S logo. They make both, sort of, their 5.56 I'm told is not quite to spec. A single round of 5.56 will not blow the gun up, thousands probably won't, but you're worried, nothing wrong with that, caution is a good thing with firearms, your options are getting the chamber measured and/or reamed or firing one, inspecting, and if free of pressure signs firing a few more also inspecting until your comfortable, this will need be repeated with each different 5.56 load, perhaps even lot, I've seen big variances in M855. FYI, my M1S 1:9 16" M4 profile is massively overgassed Spikes T2 buffer helped more than I ever would've expected, H3 would probably be even better. Enjoy. |
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Well, me and my 12 y/o are having a blast with this gun, and to tell the truth, it seems to be running good.
But like you said, I am a bit concerned about the chamber. So, can my local gun shop check the chamber or is this a gun smith only type deal? Matt ETA: It, for sure does NOT have 5.56 near the markings, but on the other hand, it doesn't have .223 either. |
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Its a Model 1 Sales barrel
1/9 twist will handle up to 69gr generally, maybe 75. As another poster mentioned, even their 5.56 labeled chambers are suspected to be .223 dimensions. You could contact them and see what they say about their unmarked barrel. You "should" be ok shooting 5.56 in it, just check the brass and primers for signs of overpressure. Also I would also highly recommend putting an H or H2 buffer in it |
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There is plenty of gray area around unmarked barrels and what chamber they actually have.
A "good" smith should have a 5.56 reamer that will guarantee the chamber is to spec and safe for full pressure 5.56. (~$50) edit:-Provided the barrel isn't made out of mush metal/have some sort of structural issue. You could order a reamer yourself from Ned Christiansen (Michiguns) and be very popular among your AR owning friends. (~$200) Getting the chamber checked/corrected is certainly cheaper than a new barrel, OR You could simply swap out the barrel to a known entity. (~$300) |
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Just because it doesn't say 5.56 on the barrel isn't the end of the world, SAAMI chamber dimensions are "guidelines" and not written in stone.
A standard SAAMI .223 has .0250 freebore A military 5.56 has .0500 freebore And my Stevens 200 a Savage clone has .0566 freebore and I shoot M193 out of it all the time. A simple chamber cast will give you a lot of info before jumping the gun and reaming the chamber when it might not be needed. NOTE: the legal department at the firearms manufacturers sets the freebore limits on their firearms to prevent lawsuits. |
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Quoted:
M1S calls all their barrels 5.56/.223 so I would say they are 5.56. They are currently using ER Shaw barrels. The big difference between 5.56 and .223 is the amount of leade, or 'free bore'. You could measure that with a long bullet in a resized case. They list some of them that way on the menu to show there's an option, but on the product page there's a drop down menu that gives a choice, 5.56NATO or .223Rem. Some of their barrels are/were only availible in .223. Chrome lined bore and chamber was a 5.56 only option. I bought one 5-6 maybe more years ago, and have on occasion checked the sight since, I paid attention, my buddy ordered one about 3 years ago and didn't and was quite dismayed when his invoice said .223Rem. Point being they offer both and have. |
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