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Very informative thread. And, as an aside, BCM has OUTSTANDING customer service.
Folks, sent the upper back to BCM yesterday per their request for it to be checked out.
Based on what I learned here (in spite of myself) I expect it will check out fine.
Anybody that was thinking about the purchase of one of their uppers, I think I would use this as a big thumbs up. They are really motivated to make VERY CERTAIN that every thing is "right" with the product.
As a aggravating note having nothing to do with BCM: Shipping anything associated with a firearm has gotten to be a major PITA!!! It just re-affirms my previous opinion, if you can call it anything other that a firearm component or part, and make it stick, you are better off by miles.
woofe
Getting one that won't close on a .223 Rem 1.4696" is good.
Ideally you want 5.56mm NATO chambered guns to not close on a USGI 5.56mm NATO NO-GO nor FIELD gauge, sometimes it's hard to get one to not close on a NO-GO, but they should never close on a 5.56mm FIELD gauge.
headspaces of .223 and 5.56:
SAAMI .223 REM GO = 1.4640"
NATO 5.56mm GO = 1.4646" to 1.4648"
SAAMI .223 REM NO-GO = 1.4670"
NATO 5.56mm NO-GO = 1.4704" to 1.4706"
SAMMI .223 REM FIELD = 1.4700"
NATO 5.56mm FIELD = 1.4728" to 1.4730"
Colts FIELD II = 1.4736"
Yep, I was a happy camper when it refused to close on the 1.4696 gauge.
However that cast major suspicion on my recently purchased 5.56 NATO NO-GO gauge, which was labeled 1.4704. I had tried it on the upper and it closed as well. That really got me going.
It turns out that gauge was the same length as my SAAMI NO-GO (1.467 in) gauge when measured with my Stoney Point fixturing. Yeah, not the most accurate method of comparison on earth, but the set has served me well for a variety of reloading needs. The questionable gauge has already gone back to the MFG.
I will be purchasing another gauge or two to allow me to reliably measure the longer chambers.
woofe
Wow, you could have spent all this time shooting that rifle instead of wringing your hands over it. All this fuss over fixing something that ain't broke. :( Bummer.
I knew Paul would never sent out an out of spec upper .:D
Woofe,
We looked at your upper group. It is PERRRRR-FECT!! :D
It is NATO-rific!! :p
Folks,
Got a chance to look at this upper group and it is a perfect USGI NATO 5.56mm chamber. Please do not confuse that with a version of a SAMMI spec chamber that the commercial market likes to call NATO. They are very very different in dimensions. They are not the same.
I could see these problems at the time of the first post. But anytime a customer is concerned about saftey, I want to always confirm everything is perfect with my own two eyes.
http://img.photobucket.com/albums/v4...TONATONATO.jpg
Pictured above on a NATO NoGo. (Our headspace BCG’s have the back end of the carriers painted sliver so we can ID them.) As you can see, this upper is ready to go to WAR !!! grrr. :eek:
I have taken at least a dozen emails and phone calls regarding this subject in the last week. (Damm, a lot of people read this board.) I just hope they read the entire thread.
So this is the best advice I can give to the folks regarding this subject.
1) Even if you think you're using a NATO gauge (because Brownells said it was or Clymer or Forester or ?), it is probably not the correct gauge. It does not matter what the label says. It does not matter what the label says. (written twice on purpose) Most are labeled wrong. Many labels are even arbitrary, because the gauge company or a barrel company decided what their "Go/No Go" gauges would be within their SAMMI or NATO chamber that they are building.
2) Do NOT, Do NOT let your local gun store tell you anything about headspacing. (Virginia Arms is an exception, gotm4 gives some of the best advise on the net.) A full 99% of gun shops don’t know how to test properly, don’t know the difference between NATO and SAMMI, don’t know the proper gauge specs, they don’t know much. This also includes about 99.99% of the gun show carnival barkers.
Let the gun shops sell you a pistol, let them give you a form #4473, let them mount your scope on your deer rifle, but do not - do not – do not let them touch your AR15. As an example, Woofe showed his upper to a variety of AR15 Vendors at the gun show (and other folks), and not one single one of them were able to see the errors in the method of measure. Please don’t rely on these folk for technical info.
Of course Grant (who specializes in the mechanics of this platform) could see the error in the first post.
3) A little knowledge is dangerous, but if you must mess around with a headspace gauges get a FIELD gauge. That is the only one you will need. That is the only one you will need. Not just any field gauge, get the NATO one that Colt recommends (.1.4736”)(Brownells #319-418-033). You are not building barrels, you are not fitting bolts. You are in “the field”, and that is your gauge.
Double check the measurements on your gauge. I have seen many gauges with text and not marked with a numeric measurement and even mismarked dimentions. Get rid of them. Just keep the Colt FIELD Gauge
Woofe – enjoy your upper group!