Headspace gauges, primarily for Criterion Core

[Wake27]

I asked Criterion but didn't quite get the specific answer I was hoping for. I need to check headspace on my Criterion Core and Geissele REBCG.

"We hold tolerances that are well inside of SAAMI spec with a 1.4646 go spec and a 1.4676 no go spec. I agree, the SAAMI minimum and maximum gauges do little but ensure that your rifle is within tolerance… it does not ensure tight tolerances."

So with that in mind, does anyone have an idea on what gauges would be best? I guess he's saying anything would be better than nothing and it wouldn't hurt to have some on hand for my other ARs, but I'm trying to confirm a headspace issue with this specific setup.

[One More Time]

I have these for go.
1.4646" Colt spec
https://www.brownells.com/gunsmith-tools-supplies/measuring-tools/headspace-gauges/5-56mm-nato-colt-spec-1-4646-go-gauge-sku100010713-19183-105916.aspx?sku=100-010-713

14636" 5.56 NATO
https://www.primaryarms.com/clymer-go-gauge-5.56mm-nato-go556nato

No go.
https://www.primaryarms.com/clymer-no-go-gauge-5-56mm-nato-ng556nato

[Todd.K]

I'm trying to confirm a headspace issue with this specific setup.

Headspace problems are exceeding rare, even with the budget AR’s, what makes you think you have one?

[Wake27]

Headspace problems are exceeding rare, even with the budget AR’s, what makes you think you have one?

Three blown primers on this setup, with two different types of ammo. I have a thread on it here somewhere.


Sent from my iPhone using Tapatalk Pro

[opngrnd]

I've used Forster headspace guages. You'll have to remove the ejector and extractor from your bolt to use them, but I used the inexpensive jig from Brownells for that. They also sell the necessary roll pin punch. I purchased spare ejector roll pins from White Oak Armament, since I try not to reuse roll pins.

You can also send the upper to Criterion, and for the price of the bolt, they'll headspace a BCM bolt to your barrel. This may be the best option.

[curious1]

I think Pacific tool and gauge sells a function gauge to check the minimum chamber dimensions and I think it serves as a minimum Go gauge also.

[Todd.K]

Three blown primers on this setup, with two different types of ammo.

Describe “blown” for me.

[StainlessSlide]

PTG also makes an "Extension Headspace Gauge" that measures the chambering independently from any particular bolt. These can be seen in use on some SOTAR videos. They look like a headspace gauge with bolt-lug-like projections. You insert then into the chamber and twist them, like a bolt locking.

I have tested around five Criterion barrels with this GO gauge, and one didn't pass. It felt like the gauge would have seated with more torque. I would estimate that the datum line was only .0005 too far aft. I didn't return this barrel because the drawing gives a tolerance of -.003 on the bolt face relative to the bolt lugs. So I was pretty sure I could find a bolt that would pass the GO headspace gauge with this barrel.