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Posted: 10/18/2018 10:59:16 PM EDT
I've got this virgin barrel Bulgarian AK74 build that has me worried.
It runs fine. No issues feeding or extracting and ejecting. The empties go flying into orbit as expected. The primers on those empties have a distinct raised rim around the primer crater. And it looks like the primer is starting to back out.  Attached File Attached FileThe bolt face looks good, and the bolt lugs have no peening or deformations.  Attached FileThe barrel headspaces perfectly both with and without the carrier. The barrel is a new Bulgarian cold hammer forged barrel from K-Var, and the kit came from R Guns. I used an oversized pin for the barrel pin. |
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Posted: 10/18/2018 11:10:03 PM EDT
[#1]
Go gauge:
 Attached File Attached FileNo Go gauge:  Attached File Attached FileAm I worrying too much about this build? Are these signs of a pressure issue in this rifle? |
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Posted: 10/19/2018 1:34:50 PM EDT
[#2]
Honestly it almost looks like the primer is just "molding" to that chamfer on the firing pin hole in the bolt when it's firing. Is there excessive recoil or is brass flying forward consistently?
I don't see anything OVERLY concerning with the spent rounds after seeing that bolt face. None of my rifles have that chamfer though so i'm a little curious as to how it got there. |
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Posted: 10/19/2018 6:12:57 PM EDT
[#3]
Yeah, that's a very heavy chamfer on the bolt that appears to be allowing the primer to flow into it. None of my factory Bulgarian '74 bolts have that heavy of a chamfer on it.
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Posted: 10/19/2018 9:40:06 PM EDT
[#4]
Quote HistoryQuoted:
Yeah, that's a very heavy chamfer on the bolt that appears to be allowing the primer to flow into it. None of my factory Bulgarian '74 bolts have that heavy of a chamfer on it. If they do, what purpose does it serve? None of my Polish 47 bolts have chamfered firing pin holes. I’ve actually never seen a bolt face with a chamfer cut like this. It’s puzzling. Should I assume that it’s ok to keep shooting it? |
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Posted: 10/20/2018 7:38:53 AM EDT
[#5]
My Bulgarian AKS-74 build (parts kit circa 2005-ish, built on a tapco flat yo) doesn't have nearly that prominent a chamfer on the FP channel. There *IS* one there, on the bolt face, but it's considerably smaller.
bolt by Armed Ferret, on Flickr The gun also desperately needs to be cleaned. 
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Posted: 10/20/2018 1:43:08 PM EDT
[#6]
Here are some better pics of the boltface.
Notice there's no gas etching from the primer. So the bolt is nearly new. The firing pin head doesn't wobble at all through the bolt face. I've taken a couple of pics with the flash to show how deep the chamfer is.  Attached File Attached File Attached File Attached File Attached File |
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Posted: 10/20/2018 5:21:15 PM EDT
[#7]
damn that firing pin protrudes significantly too.
weird. |
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Posted: 10/20/2018 7:12:02 PM EDT
[#8]
Quote HistoryQuoted:
damn that firing pin protrudes significantly too. weird. |
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Posted: 10/21/2018 10:48:05 AM EDT
[#9]
Quote HistoryQuoted: The chamfer makes it look that way. ) and realized the chamfer may have made it appear more sticky-outy than it really is.
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Posted: 11/5/2018 11:09:00 AM EDT
[#10]
Primers look pretty normal for an AK-74 with surplus ammo in my experience. Was a concern when I built my first one like 15 years ago, the primer flow looked unusual to me as well, only to find out it is common. Just more AK "slop" in the tolerances I guess. All mine are correctly headspaced, matching S/N builds, and work as the Bulgarians intended them to- just not for whom they were intended.
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Posted: 11/6/2018 1:12:25 PM EDT
[#11]
My bulgy 74 build does the same thing.
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Posted: 11/6/2018 8:53:01 PM EDT
[#12]
The firing pin hole chamfer is a little too generous, causing what you see. Nothing really to worry about.
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Posted: 11/6/2018 9:22:09 PM EDT
[#13]
OP
My factory built Bulgarian AK does the exact same thing. My bolt face is chamfered almost identically to yours. I have had it since 2009 and fired approximately 3000 rounds out of it. I have never experienced a problem with the extra chamfer on the firing pin hole. |
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Posted: 11/10/2018 8:53:27 PM EDT
[#14]
I'm thinking that the chamfer is designed to deal with primer pocket sealant build up.
I can't think of any other reason why there's a chamfer there. |
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