Range Report, 2 new ARs

[Guest gcrookston]

By dumping a couple old Army pistols last month, I got a few new ARs to shoot this month.

The first is a CMMG Mod4 SA equipped with an EOTech 553 and 3x Magnifier.... 500 rounds of M193 LC99 were shot through this gun. I could try to go into details, but let me just say "WOW, GREAT!", This gun wasn't cleaned during the shoot, we had zero malfunctions and with expectant combat accuracy, it delievered on target with 2 to 3 moa over a range distance of from 100 to 500 metres. I want one! (oh, ya, I already have one!).

The 2nd up was a Bushmaster varminter.... I put a Burris 3x-12x XTR on it with a GG&G QDM... and after feeding it 60 rounds to season the barrel with groups averaging 1.9MOA, it failed with burst case. upon examining the other cases, we could find no indication of a head-space issue (i.e. no bulging primers or case). Switched to Black Hills 77 gr with marginal results, then to 62 gr FGMM 62 and started tack driving in the 0.50 to 0.75 MOA groupigs.... after 52 rounds, another ruptured case, this time it included a broken firing pin, and half the case still in the chamber.

Still, the spent brass do not indicate a head-space problems other than the two encountered... Guess I'll need to have this one checked out...

[Guest Mugster]

Well, thats a bummer. Check it with a set of .223 and 5.56 headspace gages and see what you get. The other thing to measure is the diameter of the fired brass. You could compare it to the other rifle's ejection or post up, I can measure some of mine if you want.

Look like a couple of pretty nice rifles.

[Guest superslacker]

My first AR was a Bushmaster, and it was a jam-o-matic. I could only use certain types of ammo and certain magazines. I took everyone's advice that I could talk to, but finally traded it in for a Rock River m4 and have never had 1 problem since. I think bushmaster has quality control problems, for whatever reason.

[Guest gcrookston]

The Bushmaster is marked "Rem 223 / 5.56 Nato" -- I would take that to mean either/or. I know diamentionally and pressure-wise the two rounds differ just a wee bit, and SAMMI spec 223 guns are not always comfortable with 5.56, but that 5.56 is always comfortable with Rem 223.

I personally have shot both types inter-changibly in a Savage bolt (.223) , HK93 (5.56) and other ARs (.223 and 5.56) ,without issue.

With the exception of the Black Hills, all ammo was new manufacture loaded to Nato 5.56 standards (USGI surplus), while the Black HIlls was remanufactured. Yet we didn't have a failure with the Black Hills.

It's the only thing I can think of that would cause this problem: that being the chamber is out of spec.

I don't have any calipers, and have written Bushmster for an opinion and am waiting their reply. I would think at the very least this would be a warranty issue and perhaps they will be kind enough to send me a new barrel, at the worst, I return the rifle to them for examination and correction.

I've never had this type of failure in an AR and to experience it twice within one day's shooting leads me to believe it's gotta be the rifle, not the ammo, as the CMMG rifle was feeding the same ammo (except Black Hills), without any issues.

P.S. The Green scope was also a warrantee issue. The black scope I purchased at the store in Tacoma was all buggered up in the bell housing to the point where the sunshade could not be attached without serious mill work. I originally purchased a fixed 10x scope, but the folks at Burris, after explaining the problem, were kind enough to issue a store credit for an upgrade, as the store didn't have another fixed 10x in stock. Other than this rifle, that scope and a GG&G lense cover that didn't work, my vacation went fine....

Edited July 13, 2008 by gcrookston

[Guest Mugster]

Dimensionally, a .223 and a 5.56 round are identical. But yeah, a 5.56 chamber has a longer throat. The go guage on a set of chamber gages should be nearly the same as .223. The no go guage for 5.56 is quite a bit longer, and a 5.56 chamber will pass a .223 no go. I think they load 5.56 to 60k psi and .223's limit is around 55k, but don't quote me.

The military also uses a third gage, which is the "F*&% It, Its Time To Fight" gage. Basically if they have a barrel that flunks a no go gage, they can try the FIITTF gage on it and keep using it if they have to.

I'll bet they check headspace before they ship at bushmaster. I'd also bet your chamber is a wee bit too big in diameter towards the middle of it.

[Guest gcrookston]

Thanks Mug, maybe we can just blame Joe at Hero Gear? We could blame Dan at Hero Gear, but he's such a nice guy, he'd just smile and tell us to go F%# ourselves... Joe, on the otherhand, takes this kind of thing personally...

[Guest gcrookston]

My first AR was a Bushmaster, and it was a jam-o-matic. .

I was always a Colt AR guy, up until recently when I purchased an Armalite. I staid away from Bushmunsters for the same reason you are reporting...

This is my first bushmaster. My baby brother had one that would eat a spent case up into the receiver and jam all heck out of it. I'd sit there with my SP1 and say "oh really?".

Gotta tell you all, the CMMG has gotta be the best AR I've ever had. Reasonably priced too. I have no idea what the sticker price at HeroGear is on one of these, I traded for it. Maybe $700-800? At least the value of an old Army Pistol.

Edited July 13, 2008 by gcrookston

[Guest nitrous_mike]

So far my bushmaster has been eating wolf and brown bear just like it was high end brass, I just picked up a M&P today and will be running it tomorrow so we will see how well it likes the brown bear after I run some brass threw it.

[Guest GLOCK2340]

I have a bushmaster and it eats everything except Wolf. It will not cycle Wolf at all. I bought 500 rounds of Wolf just to try, and it has been a pain trying to cycle the stuff one or two rounds at a time and then another hang up. Not one problem with any kind of other ammo.

Edited July 13, 2008 by GLOCK2340