Headspace concerns

[evanh]

This is the 6th BHW barrel of mine, second 308. Finally getting around to assembling the gun, and checked the headspace. The first 308 I built, I used clymer gauges and the bolt did not close on the no-go. Now this second barrel, closes on the no-go. So I bought a clymer field gauge and it does not close. Reading on here today, one post mentioned that someone else mentioned, clymer's aren't recommended for this chamber? I have been having no luck with contact from BHW, sent an email, called and left a message, facebook messaged. Kinda annoyed with that. 

I bought another bolt, and it does the same thing. Original bolt is Lantac. This bolt is JP Rifles. Same clymer gauges... The other 308 barrel was with a Lantac bolt.

I'm using the method as I have in the past of removing the ejector and extractor and checking the barrel and bolt, in hand. Much like how the Brownells video shows. 

Looking for insight.

[GLSHOOTER]

I'd try a few more phone calls but I have seen HS gauges have issues with the chamber BHW uses. In firing checking for shoulder movement no one has ever came up with an oversized chamber. Using a new factory round everyone has been fine. I've shot quite a few and have a couple of them and everything fired comes out right.

I know what I would do but you'll have to decide for yourself. Also I've found that at times their Facebook page is a good point of contact.

Greg

[evanh]

So, basically assemble and take a few before shot brass measurements, and after shot brass measurements? How many shots, like 3-5 for a good average? How much movement would I be looking for? New brass isn't quite shaped to the chamber, right? Would my headspace comparator read correctly from new, to fire-formed? I have the Hornady set. Would there also be a different, recommended headspace gauge that works with the 308B chamber? Not the clymer's. 

Thank you for the response.

[GLSHOOTER]

I feel three shots with every barrel. That gives me a nice average. I use the Hornady tool to take my numbers. All we brass will be undersized. If you manually run a few through the chamber they should death and extract fine. I just drop them in the chamber and close the big by hand with the upper off.

Once you get your cases that are fired do your comparison to other known good chambers you have fired cases from. They will be very close within 0.002 - 0.004.

I have found these big frame ARs cause guys fits with HS gauges. I never worry much as the chamber would have to be like the Grand Canyon in depth to cause a case failure on the first shot of new brass. I see MANSON gauge to set HS on Savage 308 based rifles but there I control how big I want to go but if course here we don't have that option. I believe BHW uses PT&G reamers and gauges but I have not heard what lately.

Greg

[evanh]

Alright so I finally made it out to start with break-in. I took numbers down, but I'm not sure how to feel about them.

All the big numbers would be minus 2.009". Using my mitutoyo dial calipers the "Zero" is 2.009". Using the Hornady D400 comparator. I did check the bore and it is .400".
I also measured all three of my Clymer gages. Go, No-Go, and Field. I also checked with a pair of cheap digital calipers, zeroed, and the numbers are within a thousandth.
"Go" - 3.635" (gage says 1.630")

"No-Go" - 3.6385" (gage says 1.634")

"Field" - 3.644" (gage says 1.640")



Federal Gold Medal 168gr - avg of 5 cases using Hornady headspace comparator

Avg before firing - 3.6294" = 1.6204
Avg after firing - 3.6418" = 1.6328
Cases grew an avg of .0124"



Gorilla hunt ammo with federal cases - avg of 5 cases

Avg before firing - 3.6312" = 1.6222
Avg after firing - 3.6424" = 1.6334
Cases grew an avg of .0112"



Same Gorilla ammo box with 5 casings shot from a non blackhole barrel

Avg before firing - 3.6312" = 1.6222
Avg after firing - 3.6374" = 1.6284
Cases grew an avg of .0062"



Sig Marksman Elite 168gr OTM - avg of 7 cases

Avg before firing - 3.6338" = 1.6248
Avg after firing - 3.6417" = 1.6327
Cases grew an avg of .0079



Hornady tap from the my other 308 Blackhole barrel

Avg before firing - 3.6335" = 1.6265
Avg after firing - 3.6381" = 1.6291
Cases grew an avg of .0046"