Loose Muzzle Brake

[Clucknmoan]

Working up a load today and had something interesting happen. Wondering if what I saw is consistent with what you all have seen.

Shooting .5 grains at a time to find max pressure with RL26 and 140 Bergers in my 6.5x284 and looking for flat spots in velocity along the way.

Shot sighters at Target #1, one of each charge at .5 increments from 53.5 to 56.5 grains. As you can see, all shot fairly close with the exception of the last one, went high and left. Figured it was just dead on a scatter node or I pulled it.

Moved on to shooting 3 shot groups around some of the flat spots I found during pressure test. This is where the head scratching started. Groups 2 through 5 all shot 2 together and then spit one way out and they followed the POI of the "flyer" during the pressure test. Kept adjusting my hold and could not figure out why in the heck the group POI was so far out of the pressure test POI and why in the heck the flyers were so bad.

Right after group 5 was shot, I was literally scratching my head and looked down at my brake, it was loose by about 1/8 turn. Tightened it up again and had one more group to shoot, not a great group, but the POI shifted back to a reasonable location and the flyers went away. It must have cone loose on that last sighter on target #1.

I can see the loose brake causing a POI shift, but I am still dumbfounded about how it woild shoot 2 together and then spit 1 way out.

Ever see this? I am pretty tempted to shoot a seating depth test with 55.5 grains or so, but maybe I should scrap the whole test knowing what I do now.

 

[rijndael]

I've seen the same 2+1 group with a loose brake. My brake is one of the self timed ones, and the ports maintained their orientation, so I didn't figure it out until I got home.

 

[snert]

Yep, seen it, done it. Mostly caused missed groundhogs, but I redid the test later to the groundhog's dissatisfaction.

re-do the test. Induced a variable that you can't account for

 

[dmoran]

Didn't tighten a barrel enough once, and basically seen the same thing.
Bad harmonics and/or what ever all....
Donovan

 

[K22]

A loose break will cause erratic patterns according to my gunsmith who installed mine on my 308. I've never experienced it since I always make sure it is tight.

 

[nmkid]

The brake on my last rifle kept coming loose so I put some blue Loctite on the threads and the problem was cured.

 

[Metal God]

I've never had any of my muzzle devices come loose ( Likely just lucky )
I've heard of muzzle pull off that can effect POI but I believe that when the air being pushed out of the barrel in front of the bullet hits the brake and causes POI shifts . I did not realize a loose muzzle brake could cause the same thing . Makes sense though seeing how that must effect harmonics . The consistency seems a bit odd though .

Check these groups out . Do you think I'd ever really known there was a problem if I only shot 3rd groups . These were all shot during load development . and although I had seen these double groups come up from time to time I figured it was me . Then one day I shot that bottom pic which is a 10 round double group . No way that was a normal thing .

Anyone want to guess what the problem turned out to be ?????

 

[Homerange]

I've never had any of my muzzle devices come loose ( Likely just lucky )

Anyone want to guess what the problem turned out to be ?????

Loose action screws.

 

[Clucknmoan]

Alcohol?? Were you seeing 2 targets?

 

[Sniper338]

Ive had them come loose. I just learned to snug them or check them everytime I pull a gun out of the safe

 

[Homerange]

Loose action screws.

It's unusual that two groups was the result....they can't have been very loose like a cheap Rem 7mm08 that I got. With FL it horizontally strung ~1 1/4" @100yds with minimal vertical. Someone before me had F'ed with it and to tighten the main screw properly meant you couldn't open the bolt.
Filed 1/16" off the main screw and with FL's, 5 shots went just over 1/2".
Handloads it cloverleafs. It's still a cheap and very plain rifle but it shoots plenty good enough for deer.

 

[Metal God]

.they can't have been very loose

15lbs in the front 5lbs in the back . FWIW the manufacture recommends 40lbs on both . My torque test showed my rifle liked 35lbs in the front 30lbs on the back .

NOTE : This was a Savage model 10 with accustock which have a unique bedding system . The systems design may have been a huge factor in the results .

 

[Metal God]

OK , it appears to me there are multiple ways to get these double groups . The OP is only shooting 3 shot groups which at least in my case . My groups would have looked exactly the same as the OP but my issue is not muzzle brake related . Are we 100% sure it's the muzzle brake that is causing this issue ? I think some controlled larger groups tests are in order to rule out some things ???? yes/no

 

[CharlieNC]

You had yourself an uncontrollable tuner!

 

[Clucknmoan]

I will be shooting the entire test over again tomorrow, with a tight brake!

Yes it's only groups of 3, I'm just trying to find the general outline of the node. After that I will work on seating, then come back and shoot larger samples in smaller powder charge increments.

I'm sure it could be a lot of things that's causing this. But it's way to much of a coincidence that I shoot 5 shots each .5 grains apart, the group stays under .6". The crazy crap starts happening, then I tighten the brake and the last group (even though its obviously out of the node) comes back to where it should be. No major fliers. Just too suspicious to me.

Thanks for all the replies, I will post results.

 

[Metal God]

You had yourself an uncontrollable tuner!

If this was directed to me I'd agree that when ever a issue comes up it's uncontrollable until it's identified then controlled for further testing to determine for sure that was the actual problem . Until a problem is identified it will be uncontrollable which mine was for 6 months until I figured out it was the action screws . Once tightened and Loctite applied I've not shot a double group since , That's about 1500rds or so

 

[butchlambert]

15lbs in the front 5lbs in the back . FWIW the manufacture recommends 40lbs on both . My torque test showed my rifle liked 35lbs in the front 30lbs on the back .

NOTE : This was a Savage model 10 with accustock which have a unique bedding system . The systems design may have been a huge factor in the results .

Are you sure it is Ft Lbs? How about inch Lbs?

 

[Metal God]

I did not say but this was inch lbs sorry should have been more clear . I just assumed we all knew action screws are not torqued to foot lbs . I guess you could , so lets say they were 1ft-lbs front , 1/3 ft-lb back ish . Inch lbs can be more precise and is why it's better in this application IMHO

 

[butchlambert]

I did not say but this was inch lbs sorry should have been more clear . I just assumed we all knew action screws are not torqued to foot lbs . I guess you could so lets say 3ft-lbs

Sir,
Your post says ft lbs.

 

[Metal God]

15lbs in the front 5lbs in the back . FWIW the manufacture recommends 40lbs on both . My torque test showed my rifle liked 35lbs in the front 30lbs on the back .

I see lbs but nothing that distinguishes what type of poundage .