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Posted: 4/4/2021 12:17:10 AM EDT
Check it out. It started life as a mr556. Had the barrel chopped to 10.4 put some accessories on it but nothing crazy. It was never a really accurate gun but today out of no where it started keyholeing after almost every round. Any help is appreciated.
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Posted: 4/4/2021 12:24:47 AM EDT
[#1]
When is the last time you cleaned the bore well?
Have you changed ammo recently to another brand? |
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Posted: 4/4/2021 12:28:24 AM EDT
[#2]
First question is how many rounds through the barrel? How many rounds since the bore has been scrubbed?
Who did the chop job? Type of ammo that’s keyholing? Type of muzzle device? |
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Posted: 4/4/2021 12:28:55 AM EDT
[#3]
did you change the muzzle device? What ammo are you using? Is the gas block still correctly installed?
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Posted: 4/4/2021 12:36:37 AM EDT
[#4]
Start with bullet weight appropriate the twist rate - light bullets like slower twist rates.
Next, is the barrel properly crowned from the chop..this is a huge factor as the bullet is barely stable as it is and short barrels exaggerate this factor. Next..clear your rifle barrel report back.... |
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Posted: 4/4/2021 12:44:39 AM EDT
[#5]
Barrel is cleaned spotless. With copper removed. Muzzle device is aac 51t with a m42k suppressor. When I started to notice the keyholeing I took off my can though. Gas block correctly installed with the roll pins. The barrel was chopped by a experienced gunsmith. I now chop and thread my own barrels. I took off the muzzle device and the crown isn’t very pronounced. I normally put some target crowns when I do chop and threads because why not. This rifle looks to have a flat crown. I’ll crown it tomorrow and report back.
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Posted: 4/4/2021 12:46:10 AM EDT
[#6]
As far as ammo goes I first noticed it while shooting Tula. When I had my oh shit moment I went to some hornaday frontier 62gr stuff. Only had those two types of ammo on me so that’s all I tried.
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Posted: 4/4/2021 1:23:26 AM EDT
[#7]
take the muzzle device off and shoot it with a bare barrel. if it goes back to normal, then you know something is wrong with whatever is strapped to the muzzle.
If it is still not stabilizing the bullets, then I would look at at a few different ammo types, and then approach a recrown. |
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Posted: 4/4/2021 8:40:34 AM EDT
[#8]
I'll bet whoever cut the barrel didn't cut it straight. Re-crowning won't help that.
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Posted: 4/4/2021 11:06:02 PM EDT
[#9]
Update. Recrowned the barrel and it is shooting great again!
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Posted: 4/25/2021 8:10:17 AM EDT
[#10]
Ive cut several barrels over the years with hacksaw.........didnt affect accuracy from what I could see...........Ive seen articles where they cut them down in increments to test muzzle velocity and just saw them off too...........Something like cutting one down and not crowning would cause keyholing like seen in the pictures............
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Posted: 4/25/2021 8:45:03 AM EDT
[#11]
Quote HistoryQuoted: Update. Recrowned the barrel and it is shooting great again! Great! I'm ignorant of such things, but even knowing that gases differentially escaping at the muzzle can cause the bullet to 'tilt' as it leaves, I find it hard to believe that a slight difference could overcome the gyroscopic effect of a bullet spinning at 300,000 rpm to cause that kind of keyholing. I mean, gases swirl a lot inside a suppressor. Proof is in the pudding, eh? |
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