AR 15 Guru question.

[Shovelhead]

OK let me see if I can set this up so it's understandable.

What I have:
New upper builds

Seekins SP 223 Billet Upper
Black Rain Billet Upper
Seekins 16" 300 BO barrel
Rainer 223 16" barrel
CORE15 Nib-X BCG
CORE15 Charging handle
PSA Premium BCG
PSA Charging handle

The problem:
The Seekins 300 BO barrel when installed in either lower will not "seat" the BCG all the way home. The rear of the BCG
has 3/16" to go therefore the upper wont close/mate to a lower.
However, the PSA BCG with either upper and either barrel functions and seats as it should.
Next However... any combination of barrel and BCG functions fine with the PSA BCG.

So my thinking is could the Nickel Boron be playing into a fit/finish issue? But the NibX works fine in the 223 barrel in either upper.
Then you think maybe the 300 BO barrel as in either upper it fails to work unless you use the PSA BCG??????

Any guru ideas, I've run out of combinations. I do have another NbiX BCG coming....

unless I go bonkers before then............

 

[atljetmech]

AK

 

[Shovelhead]

AK

LOL... commie

 

[Shovelhead]

Where you at B.A.? Get me an answer.....

 

[b.a.customkydex]

Sounds to me like something is up with the cam pin

Where in Cumming you at? I gotta see this to wrap my head around it.

 

[Shovelhead]

I'll post a picture... I'm not far from the fair grounds

 

[Shovelhead]

OK the 223 barrel works in either upper and either BCG.
The Nickel Boron BCG doesnt work in the 300BO barrel in either upper
the PSA Premium BCG works in any combination

300BO in Seekins upper with NiBx BCG

300BO in Seekins upper with PSA BCG

300BO in Black Rain upper NiBx BCG

300BO in Black Rain upper PSA BCG

 

[CBeck]

Swapped the bolts with the carriers to see if that eliminates the carrier as the problem?

 

[b.a.customkydex]

Swapped the bolts with the carriers to see if that eliminates the carrier as the problem?

That was my next thinking.....or try just the bolt and carrier in the barrel outside the upper.

 

[mtdawg169]

I think you've got a tolerance stacking issue with the NIB bolt. There's only a few thousandths of clearance inside the barrel extension. If the NiB bolt lugs are too long or the depth of the extension is too short, the bolt may be binding up and unable to lock.