Could this barrel crown affect accuracy?

[bikemutt]

I have an AR57 upper which I've been underwhelmed with so far concerning accuracy. I guess I expected sub-MOA, or at least MOA out of it. Some groups will hold together decently then one round just disappears, can't find a hole.

I'd already posted up about how poorly it shot with a suppressor attached. I gave up on that for now and replaced it with both the OEM flash hider and a Seekins brake.

I was getting ready to take it the range today when I noticed how scruffy-looking the crown is; it rough enough that running a thumb over it will cut the skin. I tried to get a close up picture which seems to more or less allow me to share what I'm seeing in person.

I'm a novice rifleman so I always blame the shooter first but, this is not a hard kicking rifle, the AR15 lower has a very nice Geissele two-stage trigger installed, and I'm using premium FNH 40 grain ammo. The upper is scoped with a nice piece of 3-9x40 Nikon glass.

I don't have proof-positive of this yet but the same upper with a 6" barrel strikes me as more accurate than this 16" upper.

Could a rough crown like this affect accuracy?

Thanks THR.

 

[Jackal]

Yes, it definitely *could, but whether it actually does affect accuracy or not, can only be found out by benching it.

 

[rcmodel]

Sure looks bad.

Run a Q-Tip around the inside next to the rifling and see if any cotton fibers stick to anything.

If they do, it is definitely a bad crown job.

rc

 

[taliv]

while the crown looks horrible, the part that would really worry me is that ring around the inside

it almost looks relieved in there

 

[Float Pilot]

Yeap re-crown that darn thing....

 

[Reloadron]

while the crown looks horrible, the part that would really worry me is that ring around the inside

it almost looks relieved in there

Yeah, like a lip. step or shallow counter bore. Whatever, it doesn't look very good from what I can see.

Ron

 

[bamajoey]

This is a good example of a bad crown on a 22

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[Welding Rod]

Wow, looks like a M1a SOCOM crown I had.

 

[Geno]

Wow, my SOCOM muzzle did not look like that. I would have a gunsmith look at it.

Geno

 

[lxd55]

yes that crown can/will have an effect but that you said "some groups hold together" leads me to think there could be other issues.

 

[CB900F]

Bikemutt;

Just take it to a good smith and have it recrowned. Considering where you are, there should be no problem at all finding a first-class smith who can do it without fuss or overcharge. The going rate around here is about $50.00 for a target crown. The actual machining takes about 20 minutes including set-up time. Anybody who quotes you over a week to do the work needn't get your money.

900F

 

[bikemutt]

Bikemutt;

Just take it to a good smith and have it recrowned. Considering where you are, there should be no problem at all finding a first-class smith who can do it without fuss or overcharge. The going rate around here is about $50.00 for a target crown. The actual machining takes about 20 minutes including set-up time. Anybody who quotes you over a week to do the work needn't get your money.

900F

Just got back from gunsmith; she's re-crowned. Will be at the range this afternoon and report back.

 

[dprice3844444]

#1 looks like garbage #7 was done with incorrect dull bit manually run,then touched up with a manual hand held deburring tool

 

[CB900F]

Bikemutt;

I think it's highly likely you'll be pleasantly surprised by the difference in accuracy. Pure curiosity prompts me to ask what you paid for the job.

900F

 

[rondog]

IMO, whoever threaded the barrel and fitted the suppressor should have recrowned it then. It might have been that person who buggered it up.

 

[SEDurbin]

Looks like the results you would get by running a static (dead) center in the bore while threading the barrel.

 

[bikemutt]

IMO, whoever threaded the barrel and fitted the suppressor should have recrowned it then. It might have been that person who buggered it up.

Barrel was factory threaded, and I agree, they buggered it up.

 

[bikemutt]

Bikemutt;

I think it's highly likely you'll be pleasantly surprised by the difference in accuracy. Pure curiosity prompts me to ask what you paid for the job.

900F

Well, I am beyond thrilled with the results

Today was a much better day at the range. I knew something was going to be different when I shot the rifle with the ONLY change being the proper crowning of the barrel; it took me 10-12 shots to even figure out POI at 50 yards.

I started out with no muzzle device, just a thread protector.

Once I got the scope dialed in (it needed to come up about 15" or so and left about 12" or so), I was able to get off a a couple 1" 5-shot groups using Federal 40 gr ammo. Then I switched to FNH 40 gr which is hotter, POI shifted up about 1" which I think may be more related to me not controlling the more noticeable recoil (OK, it's user-flinch).

Next I mounted the suppressor and bammo, right on target, and more accurate than un-suppressed with the FNH ammo. Did not even have to adjust the scope! I did not have any Federal left so I finished off the box of FNH and called it a very good day!

Certainly well worth the $30 to crown it!

As an aside, I brought my AR57 pistol (6" barrel) with me to the gunsmith, we inspected that one and it appears to be crowned properly. I think this was a Monday hangover rifle, good to know it was easily corrected.

Did I mention I'm thrilled? LOL.

Thanks for all the help guys

 

[Legionnaire]

Thanks for the range report. I love a happy ending!

 

[CB900F]

Bikemutt;

So you found a bored & retired Boeing machinist who gunsmiths now, gave him a couple of "I intensely dislike Lockheed" bumper stickers, and plied him with a six-pack of fair decent beer huh? How else would you get it done that quickly for that amount of money, he asks.

Congratulations! Glad it all worked out. That solutions was almost certainly quicker and probably cheaper than returning it to the OEM. Less headache time too.

900F

 

[bikemutt]

Bikemutt;

So you found a bored & retired Boeing machinist who gunsmiths now, gave him a couple of "I intensely dislike Lockheed" bumper stickers, and plied him with a six-pack of fair decent beer huh? How else would you get it done that quickly for that amount of money, he asks.

Congratulations! Glad it all worked out. That solutions was almost certainly quicker and probably cheaper than returning it to the OEM. Less headache time too.

900F

That's a good one CB900F, lol.

Actually my guy is a retired veteran whom I make sure to stay on very good terms with. He feeds off challenges, when I texted him that picture of the muzzle "crown" he said "come on over, lets get that fixed".

He used a very expensive tool designed just for this purpose; creates a perfectly flat muzzle face, puts an 11 degree crown on the inside, and a gentle chamfer on the outside. Total time spent was about 30 minutes.

BTW, I shared this story with the gun dealer who in turn shared it with the manufacturer, I don't know the outcome. I did learn from the dealer though, I'm not the first one to complain about accuracy with these uppers. Hopefully the manufacturer will make improvements as needed. These rifles come with a flash hider that is all but impossible to remove, loctite I believe, or RockSett. I had my gunsmith remove the one from mine, had I not done that I would have never seen the crown. Whoever installs the flash hiders needs to be promoted to flash-hider-installer/muzzle-crown-inspector.

 

[Reloadron]

That's a good one CB900F, lol.

Actually my guy is a retired veteran whom I make sure to stay on very good terms with. He feeds off challenges, when I texted him that picture of the muzzle "crown" he said "come on over, lets get that fixed".

He used a very expensive tool designed just for this purpose; creates a perfectly flat muzzle face, puts an 11 degree crown on the inside, and a gentle chamfer on the outside. Total time spent was about 30 minutes.

BTW, I shared this story with the gun dealer who in turn shared it with the manufacturer, I don't know the outcome. I did learn from the dealer though, I'm not the first one to complain about accuracy with these uppers. Hopefully the manufacturer will make improvements as needed. These rifles come with a flash hider that is all but impossible to remove, loctite I believe, or RockSett. I had my gunsmith remove the one from mine, had I not done that I would have never seen the crown. Whoever installs the flash hiders needs to be promoted to flash-hider-installer/muzzle-crown-inspector.

Like one of these? Actually a 79 degree cutter and since 90 - 79 = 11 you get an 11 degree muzzle crown. I have used the linked cutter and it really does a nice job. They really aren't that expensive, you run a few jobs with the cutter and the pilots and they pay for themselves pretty quickly.

Ron