Headspace checks

[SiGfever]

Hello,
I have been having an issue with checking headspace on my Colt Trooper barrel (removed) and my new BA "Hanson" 16" barrel that I installed in the Colt. I bought a set of Clymer "Go/No Go" (223 Rem) gauges from Brownells and removed the bolt ejector to test. The Go and No-Go gauges fully seat on the Ballistic Advantage with the bolt installed in the Colt BCG. Since the Colt barrel is removed I can just use the bolt to check the fit. Both gauges go in an will turn, my understanding is that the No-Go should not turn?. Does this mean that both barrels are out of spec, or is the Colt bolt? Or is the 5.56 chambers the reason the gauges both fully seat, and/or turn? Sorry for having to ask such rookie questions but this is my first barrel change.
Thanks,
John

go_nogo.jpg

[SteveL]

You need a set of 5.56 gauges or a military field gauge to check a 5.56 chamber.

[SiGfever]

No wonder I have been chasing my ass, thanks for the reply. I will order the 5.56 Clymer set.

https://www.brownells.com/gunsmith-t...76-191550.aspx

[SiGfever]

Well it is amazing what happens when you get your ass out of your head and order the correct tools. The Clymer 5.56 Go/No Go set worked perfectly. SteveL, thanks for telling me what I needed without emphasizing just how much of a dumb ass I was.

Clymer556Go_NoGo.jpg

[M4C]

I thought the only significant difference was in the leade? If I'm not mistaken, closing on a .223 no go makes it closer than we would like to closing on a 5.56 no go, especially if it's not a well used barrel and bolt.

[SteveL]

Well it is amazing what happens when you get your ass out of your head and order the correct tools. The Clymer 5.56 Go/No Go set worked perfectly. SteveL, thanks for telling me what I needed without emphasizing just how much of a dumb ass I was.

Clymer556Go_NoGo.jpg

You're welcome.

I thought the only significant difference was in the leade? If I'm not mistaken, closing on a .223 no go makes it closer than we would like to closing on a 5.56 no go, especially if it's not a well used barrel and bolt.

http://www.ar15barrels.com/data/headspace.pdf

[Eric D.]

From what I’ve seen go and no-go gage dimensions are arbitrary among different mfgs and thus pretty much worthless unless you’re a barrel maker.

1.4736” is the Field dimension and that’s what I use.

Whether or not these commercial gages are actually within the 0.0002” a lot of them claim is a whole other issue...

[sinister]

Forster article:

https://www.forsterproducts.com/pdf/brochures/nato1.pdf

...and another:

http://ar15barrels.com/data/headspace.pdf

For civilians and cheap bastards like me who actually reload spent cases for multiple rifles and carbines, I'd rather have minimal-sized cases for longevity and cross-platform compatibility. Individual military rifle and carbine cartridges just have to fire and function once -- and once safely fired that piece of brass is ejected overboard, of no use or care of the weapon firer.

[elephantrider]

From what I’ve seen go and no-go gage dimensions are arbitrary among different mfgs and thus pretty much worthless unless you’re a barrel maker.

1.4736” is the Field dimension and that’s what I use.

Whether or not these commercial gages are actually within the 0.0002” a lot of them claim is a whole other issue...

Where headspace gages are useful IMO, is when you can cross check them using a headspace comparator and calipers. Then you can see where your rifle headspace is in relation to your ammunition, and visa versa.

[Eric D.]

I follow you. I have the hornady comparator and use it for my reloading. The only issue I have with it is not knowing the exact diameter of the datum line where the bushings contact the case shoulder. That diameter is supposed to be 0.330” but all the bushings I’ve seen have a radiused or chamfered edge on the end of the bore and it’s obvious that the contacting datum diameter is not the 0.330” that it should be, even if only a few thou larger, so the bushing meets the case shoulder deeper than it should and it produces a false hs measurement. If I use the comparator to measure my field gage I get a value less than the 1.4736” the field gage should be. Now, if I assume the field gage is made to the specs it claims I could theoretically use it’s known size to “correct” or “calibrate” the hornady comparator which I know doesn’t produce correct absolute measurements, only relative ones.

Where headspace gages are useful IMO, is when you can cross check them using a headspace comparator and calipers. Then you can see where your rifle headspace is in relation to your ammunition, and visa versa.