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Discussion Starter · #1 ·
I had a visit from my BIL & he brought several rifles to sight in. One AR defied our attempts. From the bench at 50 yds. the best either of us could do was 5" - 6" groups. My eyes are no longer iron-sight friendly but they aren't THAT bad. We finally gave up & as I was gathering up the brass I noticed rings or steps in the shoulder of the case. This was with 2 different loads, PMC 55 gr. & 62 gr. green tip. Just to be sure it wasn't an ammo problem I fired both loads thru one of my AR's & the brass looked normal. I'm guessing there was some problem with the reamer when the chamber was cut & it'll take a new barrel to fix it. Any insight anyone can offer would be appreciated.
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The Hog Whisperer (Administrator)
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Yeah that's pretty ugly. I would speak to whoever manufactured the barrel, if that is an option.
 

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Really ugly application of roughing reamers. Junk barrel.
 
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I had a visit from my BIL & he brought several rifles to sight in. One AR defied our attempts. From the bench at 50 yds. the best either of us could do was 5" - 6" groups. My eyes are no longer iron-sight friendly but they aren't THAT bad. We finally gave up & as I was gathering up the brass I noticed rings or steps in the shoulder of the case. This was with 2 different loads, PMC 55 gr. & 62 gr. green tip. Just to be sure it wasn't an ammo problem I fired both loads thru one of my AR's & the brass looked normal. I'm guessing there was some problem with the reamer when the chamber was cut & it'll take a new barrel to fix it. Any insight anyone can offer would be appreciated. View attachment 105715
I get cases look like that if the fire forming charge is insufficient
 

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Discussion Starter · #8 ·
I get cases look like that if the fire forming charge is insufficient
Since both loads were factory loads, & looked OK when fired in my rifle, I don't think that's the issue here. My BIL was going to see about having it looked at under the warranty, but I haven't heard anything back from him about it yet. He's on the road a lot for work so I'm guessing he hasn't had the chance yet.
 

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A reamer is most worn at the shoulder 'corner'. That dulls first. A roughing reamer has had three bad, shoulder only re-grinds that left steps in the shoulder. Normally, the finish reamer would take out the steps and increase chamber size to clean it up to SAAMI specs.
This barrel must headspace ok with the nasty, undersized, stepped shoulder or maybe its headspacing on the corner of the shoulder where its undersized. It ain't right!!
 

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Discussion Starter · #10 ·
A reamer is most worn at the shoulder 'corner'. That dulls first. A roughing reamer has had three bad, shoulder only re-grinds that left steps in the shoulder. Normally, the finish reamer would take out the steps and increase chamber size to clean it up to SAAMI specs.
This barrel must headspace ok with the nasty, undersized, stepped shoulder or maybe its headspacing on the corner of the shoulder where its undersized. It ain't right!!
I did try chambering the fired cases in 2 different AR's. The bolt wouldn't close in either of them - in fact I had to knock the cases out of the chamber with a cleaning rod - So the chamber must be on the large side already.
 

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The Shadow (Moderator)
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What in the world is that longitudinal marking? Looks like it leaves a shadow it's so deep.
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