Not head spacing correctly

[Dirty Steve]

New build .223W.  New Criterion 18 in Hybride Nitride rifle length barrel.  New Fail Zero M16/4-01 NH BCG.  (M16 version says compatible with "most" 5.56, .223, and .300 black)[could be the obvious problem]

 

New Clymer .223 and 5.56 Go/No Go guages.  

Have BCG from FZ bought 2 years ago. Same coating.  Lookis identical.  Old BCG headspaces just fine in the new set up.

Issue:

Bolt sluggish to into battery with empty chamber. Also sluggish with striped BCG.  Difficult to get out of battery and more difficult to get out of battery with Go gauge.  Go gauge will close into battery with persuasion.  Bolt much tighter inside the carrier.  

I lubed it inside and out. 

Tried the bare bolt by itself.  Difficult with barrel mount to upper.

Does the same exact thing to another AR 15 of mongrel parts.  

I left the Fail Zero customer service number ansering machine  a message tonight.  

I pulled out good calipers to see if my uneducated self could find and obvious discrepencies.  Not sure what to look for. 

 

 

[98Z5V]

4 minutes ago, Dirty Steve said:

New Fail Zero M16/4-01 NH BCG. 

Nickel Boron?  That adds to the dimension of the part.  Try a different bolt, that works in another gun.  I wouldn't initially suspect a Criterion barrel, and I would suspect a Clymer headspace gauge.

5 minutes ago, Dirty Steve said:

Does the same exact thing to another AR 15 of mongrel parts.

Use the bolt out of this one, in this build, and see what happens.

[Dirty Steve]

The Fail Zero NB BCG used in previous build from 2 yeras ago fits the new fit and headspaces flawlessly in EACH gun.  

 

The new one- not so good in either gun. 

[Dirty Steve]

It's the same as this earlier bought BCG.  This pic is from couple 3 years ago.

[98Z5V]

Same bolt and BCG, you're using in every gun?...  Did I read that right?

[98Z5V]

36 minutes ago, Dirty Steve said:

The Fail Zero NB BCG used in previous build from 2 yeras ago fits the new fit and headspaces flawlessly in EACH gun.

That wasn't coated by the same guy, at the same time, as the one that you have now...  refer back to my previous statement, here:

42 minutes ago, 98Z5V said:

Nickel Boron?  That adds to the dimension of the part.

Use the old bolt, and see what happens...  

Edited December 14, 2019 by 98Z5V

[Dirty Steve]

Issue is the new bolt.  Put the 2 year old bolt (stripped) in the new carrier and would go in and out of battery with go gauge in either .223 gun.  Put the NEW stripped bolt in the old carrier.  Would NOT go into battery in either .223.  

Here is the build.  Scope leveled.  Gun bore sighted.  Ready to fine tune on paper with the older FZ bcg in place.

Have a plain Stag Arms trigger guard but thinking about picking up a matching red Seekins Precision billet trigger guard to match the Seekins ambi safety.  Anyone ever use one??  Are they solid?  

[98Z5V]

That gives you some concrete information to send to Fail Zero, on what's happening, and get a new bolt from them. I think they need to change their name to Fail(ed) Once, now.  

Nib adds to dimensions - it's a coating. You have to undersize the part, and coat UP to the dimension, within the tolerances of the part.  Or, just coat enough to stay within the tolerance on the part in the first place.  This isn't the first time we've seen something like this here, with NiB.