Loose muzzle brake changed POI but tightens groups?

supratt96

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Was at the range today shooting a KRG SOTIC. I have a PVA Jet Blast self timing brake on it. The brake is awesome at reducing recoil but I noticed something odd today. My first group was about 1.25" high and .25" left of my normal zero but very tight; less than 3/8". So, thinking I must have bumped something, I readjusted the zero. Next group was dead center and measured .217". Needless to say, I was pretty happy with that.

But then I noticed that my brake was just a tiny bit loose, so I hand tightened it. Next group was low an to the right. It was still pretty tight; a little less than 1/2", but not as good as the first two groups. I now realized that the brake was causing the shift in POI. I readjusted the zero again and shot a few more groups. All were good, but not as good as the two groups I shot with the brake loose. I decided to experiment with the last group and intentionally loosened the brake. Sure enough, the group went high and to the left again and measured .220". No doubt about it, the rifle groups noticeably tighter with brake a little loose.

Next time out I'm going to try using a different brake and also no brake at all to see if this phenomenon is specific to this one particular brake.

Anyone else experience something like this?
 

BurnOut

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The only thing I can think of is the the loosened brake allows for more favorable barrel dynamics. Other than that, I got nothin'.

How does it shoot if you remove the brake altogether?
 

AMTGMC

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Was at the range today shooting a KRG SOTIC. I have a PVA Jet Blast self timing brake on it. The brake is awesome at reducing recoil but I noticed something odd today. My first group was about 1.25" high and .25" left of my normal zero but very tight; less than 3/8". So, thinking I must have bumped something, I readjusted the zero. Next group was dead center and measured .217". Needless to say, I was pretty happy with that.

But then I noticed that my brake was just a tiny bit loose, so I hand tightened it. Next group was low an to the right. It was still pretty tight; a little less than 1/2", but not as good as the first two groups. I now realized that the brake was causing the shift in POI. I readjusted the zero again and shot a few more groups. All were good, but not as good as the two groups I shot with the brake loose. I decided to experiment with the last group and intentionally loosened the brake. Sure enough, the group went high and to the left again and measured .220". No doubt about it, the rifle groups noticeably tighter with brake a little loose.

Next time out I'm going to try using a different brake and also no brake at all to see if this phenomenon is specific to this one particular brake.

Anyone else experience something like this?
Listen to what David Tubb says about brakes . Basicly all muzzle devices should be adjustable and every rifle has a happy spot. Probably something on his web site but listen to the pod cast @Lowlight did.
 

bjay

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This is why f class shooters uses device called BARREL TUNERS..its threaded like brake to tune barrel harmonic..brakes aren't diff
 

Massoud

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Our 'smith that barrelled that SOTIC used to work for a large AR company's custom shop. He mentions that the vast majority of accuracy issues there were muzzle device related. That's anecdotal of course because each had a unique set of circumstances but still informative. Glad to hear it's sub 1/4 capable for you.
Justin
 

supratt96

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Listen to what David Tubb says about brakes . Basicly all muzzle devices should be adjustable and every rifle has a happy spot. Probably something on his web site but listen to the pod cast @Lowlight did.
I listened to the podcast and this makes perfect sense. But, once you find that "happy spot", how do you lock it down? Leaving the brake loose doesn't seem like a viable solution. Do you shim it?