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Posted: 2/12/2017 1:01:14 PM EDT
Link Posted: 2/12/2017 2:05:32 PM EDT
[#1]
I believe I have seen others here have the same thing happen. Just like different torque values on the action screws I suppose.
Link Posted: 2/12/2017 10:52:59 PM EDT
[#2]
Been curious about this too but never looked into it much or did any comparisons too see if i could determine an impact...tag for a later read.
Link Posted: 2/13/2017 10:40:31 PM EDT
[Last Edit: FALex] [#3]
Changing the torque spec on your FH or MB can 100% effect your POI.  All systems are different, and you may have an anomaly where changing the spec doesn't mess with the POI, but I believe it will change the POI on the vast majority of rifles.
Link Posted: 2/27/2017 11:15:57 PM EDT
[#4]
Originally Posted By Eric802:
I know how harmonics can change your group size and whatnot, but can loosening your FH cause this? I took the rifle I used for the MOA challenge to the range yesterday with some ammo I loaded up - took my time with this batch of ammo, did more case prep than usual, etc., trying to get a super consistent load to re-shoot the challenge. I also loosened the FH a bit, because I wanted to try my Form 1 can on the rifle and I wanted to be able to get the FH off at the range.  

For reference, when I did the MOA thing before my average group size was .82 MOA or something like that, so the rifle is capable. This time, I couldn't get anything under an inch, and I was having stray rounds all over the target. The FH wasn't that loose; I still needed a wrench to spin it off.  But that was the only difference (other than the case prep). Same load data and everything.

So can just changing the torque on the flash hider cause this?
View Quote


What did you use to anneal? To clean the brass? Did you clean the bore? All those can dramatically change things.
Link Posted: 2/28/2017 1:15:48 PM EDT
[#5]
I have a bolt gun with bartlien barrel that has its muzzle threads cut a little off. With no muzzle device installed it shoots .5 easy. With any muzzle device, groups open up to 5 MOA. The bullet does not make contact with them, but it still significantly affects accuracy.

I'll be taking it up to PVA to get it rethreaded next week.
Link Posted: 7/4/2018 11:28:44 PM EDT
[#6]
Link Posted: 7/5/2018 12:05:04 AM EDT
[#7]
Link Posted: 12/6/2019 10:18:24 PM EDT
[#8]
Link Posted: 12/14/2019 3:05:05 PM EDT
[#9]
In my experience it does. I put a slip over XM177E1 style flash hider on an older Bushmaster 16: HBAR. I just cranked it on and that barrel was laser accurate.

I've had other barrels, that were no where near as accurate.
Link Posted: 3/10/2022 1:02:41 AM EDT
[#10]
Link Posted: 3/16/2022 1:44:05 AM EDT
[#11]
I've read that barrel tuners can make a difference with as little as 0.010" front-to-back change in their position.  So something like a brake, or any other weight at the end of the barrel that moves in closer to the barrel by a tiny amount will actually change the barrel harmonics enough to make a difference on the target.
Link Posted: 3/16/2022 4:41:36 AM EDT
[#12]
Didn't JRB do some testing or some shit like this?
Link Posted: 3/24/2022 12:11:14 AM EDT
[#13]
The USAMU used flash hiders only hand tight with Loctite to eliminate stress.

It is a known phenomenon that higher torques on muzzle devices can cause problems.

Link Posted: 3/24/2022 8:07:51 PM EDT
[#14]
I had this happen to a carbine years ago. Standard A2, great zero, 2" grouping at 100 with ball, a gorilla put on one of those FSC brakes that were all the rage. Didn't know enough to check it, go to a class, we had to zero, that thing shot about 3" at 25. One of the instructors took it off and reinstalled an A2, bam right back to normal. I don't know if it was the brake or the "extra" turn, or both.

I did have a great smith build a bolt gun and he faced the shoulder so a FH indexed at 12 hand tight and used a dab of blue.
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