Muzzle break Accuracy issue

[stan_wa]

set up
seekins percision havak element 28 nosler, trijicion tenmile scope, seekins rings, rifle and rings torque and installed per seekins manual. i got about 500 rounds down the tube so I'm not overly excited about doing a new load dev and eating my barrel life away. .
95 berger, 79 grain retumbo, .040" jump, Gunwerks brass, fed magnum primer

I recent switched from my seekins precision muzzle break to a APA gen 3 little bastard. my reason for doing this was to help spot impacts in the field. To set up the break I installed, leveled and locktied the break and torque to it felt snug. I shot prone and removed the vertical screws till I got a muzzle rise that seemed good (without using a rear bag) i landed on removing 3/4 rows of the screws. I shot about 18 shots, and recorded the Mean radius, my mean radius has increased from .27" @100 with the seekins break to .43" with the apa.
With the APA installed I can keep the target in the scope which is great but this accuracy loss is a bummer. I can reinstall the seekins break and live the the loss of target but before i do any suggestions as to why i might see such a degradation in accuracy outside of change in barrel harmonics .
odly enough inaddition to my prone group i shot 5 shots bagged on the bench with the APA installed and the 5 shot group was the worst this rifle has produced 1.5" with mean radius of .47" but perfectly vertical which I have never seen.( i know this 5 shot group is a small sample but bad stats rarely get better with more data)

 

[hereinaz]

Just spitballing…

If vertical, maybe something about the brake being new to your shooting? Different brakes are going to change recoil impulse slightly. Maybe your shooting habits are better adapted to whatever is happening in the milliseconds of the impulse.

As far as measuring a .16 difference, I mean, if you are shooting with precision like that, the smallest things will affect it. It’s why some bench rest shooters verge on the superstitious.

Shooters have seen the “tuners” help some rifles. Maybe try configurations of screws in holes? I dunno.

Ultimately, I have no experience chasing your level of precision. To me, I quit at sub moa. Maybe weigh the difference between .16 moa vs spotting shots? You got a very good thing going either way. I could see how someone pushing limits of precision could be irritated.

From my perspective, statistically, the 5-10% of shots of the .47 group that would be distributed outside of the smaller .27 group is not going to mean the difference between killing or not in 99.9% of scenarios.

 

[BBob]

If it was shooting before I'd do a quick powder ladder bracketing your previous powder charge to see if you could get it back. If you find a potential improvement I'd run the same ladder over again to see if it proves out. Shouldn't take too many shots to do this.

 

[WeiserBucks]

my mean radius has increased from .27" @100 with the seekins break to .43" with the apa.

If this information is accurate and repeatable, your groups have almost doubled in size. I would take that APA off and junk it quick, fast and in a hurry.

 

[RWT]

It’s a 28 nosler. if you hit it the first time I can’t imagine a follow up shot is needed. i would go back to the original break.

 

[stan_wa]

If this information is accurate and repeatable, your groups have almost doubled in size. I would take that APA off and junk it quick, fast and in a hurry.

That's kinds of what I'm leaning towards. I have Herd there can be a issue with too much down force on the muzzle causing the barrel to bounce. If thats the case i could try groups with differnet setting on the apa. but if that bounce is happening i cant tell.

From my perspective, statistically, the 5-10% of shots of the .47 group that would be distributed outside of the smaller .27 group is not going to mean the difference between killing or not in 99.9% of scenarios.

when i refer to mean radius that is not group size. in this case my 17 shot group with apa was about 1.3 moa and standard 10 shot gropu was about .75 moa with seekins brake. However i think there is some good truth to you point that even with the larger group is probably has a low affect on the WEZ hits calculation.

If it was shooting before I'd do a quick powder ladder bracketing your previous powder charge to see if you could get it back. If you find a potential improvement I'd run the same ladder over again to see if it proves out. Shouldn't take too many shots to do this.

this is a reasonable solution if it doenst prove out go back to the seekins break.

 

[TaperPin]

I don’t think your problem is with the brake pushing down too much. The bullet has already left the barrel when the brake starts pushing down.

I bet there are two things going on. Primarily the different weight of the brake has put your rifle out of tune - the vertical group supports this. I’d adjust seating depth to get back in tune, but not worry about working up loads from scratch.

The second thing is the bore diameter of the brake - going up a size over what’s normally used has been shown to not change the brake’s performance a significant amount, but prevents accuracy issues if the brake isn't threaded exactly right and gasses are pushing a little more on one side than the other. I’d get the barrel back in tune first in case that solves the whole issue.

I‘m looking forward to seeing what you find out.

 

[stan_wa]

The apa break is .30 cal so I can measure the id but is probably. 338 id or something.
I am thinking about trying pro 5 or a hypertap brake.
The hypertap is unique in that the baffles start out perpendicular to the bore then turn rearward. Winning in the wind has a video talking about flat baffles, oversized breaks and well aligned brakes all helping with accuracy. The self timer models will probably never be as square as smith drilled one but I’m hoping they can still be acceptable.

 

[Wrench]

If you watch setup vids on barrel work you'll see how the od and id don't always run square to each other. It's common to have some deviation. If a smith fit break is installed (correctly), the bore gets indicated, then the threads cut and finally the bore on the break can be checked. If it's not centered, there's potential for disruption. Increasing the bore size is a bandaid imo.

Try shooting through paper at 10 yards and see if there is any yaw in the bullet.

 

[Shortschaf]

Put all the screws back in and try shooting another group. If things don't improve try a different brake (up to and including your old brake).

 

[Sandstrom]

I had a break installed on an x-bolt, it greatly affected group size. First shot or two was great, after that it would start stringing vertically bad. I went round and round trying to figure it out. Long story short, the smith that installed and built the break made the bore hole too small. I chucked it up in my lathe and opened up the bore, one drill size and it started shooting like it did before the break was installed. Not sure the exact reason for it, but slightly more clearance helped!

 

[Wrench]

I had a break installed on an x-bolt, it greatly affected group size. First shot or two was great, after that it would start stringing vertically bad. I went round and round trying to figure it out. Long story short, the smith that installed and built the break made the bore hole too small. I chucked it up in my lathe and opened up the bore, one drill size and it started shooting like it did before the break was installed. Not sure the exact reason for it, but slightly more clearance helped!View attachment 648627

If the hole isn't centered to the bore the gas has an un even push on the bullet at its last bit of influence. That's why I suggest shooting paper up close. On a bad fit the bullet will show signs of yaw through the paper.

Open the brake enough and the influence isn't enough to matter. There may be a tiny bit of recoil increase....but often it is immeasurable.

 

[Sandstrom]

One drill size helped fix this!! Weird that it went up or down based on ammo.
Ryan

 

[BjornF16]

Just for clarification: How many shots are you taking for the .43” with new brake?

How many shots determined the .27” with original brake?

 

[stan_wa]

Just for clarification: How many shots are you taking for the .43” with new brake?

How many shots determined the .27” with original brake?

.27 is over about 100 shots during that time i was changing some load variables power charge and seating depth.
.43" was only over 18 shots.
I understand this is not a perfect statistical representation as i didn't track the standard deviation on all these shots. but i have shot 10+ groups of 10+ shots and measured the mean radius on all of them and nothing ever showed over .35" so i feel pretty confident the break is showing a out of family accuracy. going forward i will log mean radius and standard deviation for all shots taken so i can apply more stringent statistical confidences. ( I just didn't really know when i started why i might need that, lesson learned)

 

[stan_wa]

Put all the screws back in and try shooting another group. If things don't improve try a different brake (up to and including your old brake).

Because im interested im going to do this and try some other breaks.

 

[ArcherAnthony]

You could try a barrel tuner behind the brake. But you could also try different bullet seating depths.

 

[Darryle]

I spoke to Greg at Terminator about brake bore size in relation barrel bore size, he sent me this link.

Now, if the bore was not concentric, I understand why you had the issue. Glad you got it resolved.

 

[stan_wa]

I spoke to Greg at Terminator about brake bore size in relation barrel bore size, he sent me this link.

Now, if the bore was not concentric, I understand why you had the issue. Glad you got it resolved.

Well it’s not resolved yet haha

 

[Darryle]

Well it’s not resolved yet haha

Well, I read @Sandstrom post as being resolved.

Curious how this plays out now.