Is my brake ruining my groups?

M

Markus

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Last year I had a local Smith rebarrell my 700 Remington with a new shilen select match barrel in 300 RUM. I also had a new brake installed. I have had no luck getting the rifle to shoot better than 1.5" groups at 100 meters. Now for comparison I have a 6.5x47 that I have shot into the .2's on occasion and shoot great groups out to 300m eith it and my custom 270 as well. So I don't think it is me. My brake seems to have significant machining marks and I was wondering what you guys think of it and if this might be the root of my problems.
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You can see the machining marks in the gills. It appears the rear gill doesn't line up with the front 2 possibly but could be an illusion. and you can see the machine marks inside the brake bore. Is this probably the root of my problems?

I don't have a threaded cap to replace it with. Would it be safe to shoot a few groups without the brake on with no cap on the threaded muzzle to see what kind of results I get?
 
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I'm going to put it in the sonic cleaner and clean it real well tonight. Usually I scrub it with solvent and a brush.
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Shoot away without the brake. It will not harm the barrel.

I often receive phone calls from happy customers telling me their rifle has never shot as well as after they had the brake installed. Usually light short magnum rifles.

How well the brake is installed and the barrel crowned is extremely important for accuracy. Properly installed it should never harm accuracy, usually improves it with the heavy kickers.

I don't like the looks of your crown though... and I don't like the threaded interior of the brake...

Have a mandrel made... the first two inches about .298" in diameter, the next two inches .328" in diameter... this inserted into the bore with the brake installed should move about freely... pointed upwards you should be able to bounce it up and down... if it doesn't do that the brake is out of alignment or not bored large enough...
 
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Thanks Dennis, I will go to the range without the brake and see what happens. I should be able to turn a mandrel on my Dad's lathe too. We'll see what happens. I've left a message for the Smith to see what he figures about it. He's fairly accomplished so I'm sure he'll help me out or be able to get it setup again if there is an issue. I've just never had a Shilen select preform so poorly.
 
I just got back from his shop. We cleaned up the machining marks and opened up the bore a little further. It was only .328" so he took it to .338" I'll test it out again and see how it goes. I'll try groups with and with out the brake and see what the results are.
 
Just out of curiosity. What don't you like about the crown Dennis? And do you mean the course machining marks in the bore of the brake when you say threaded interior?
Thanks
Joe
 
joehunt said:
Just out of curiosity. What don't you like about the crown Dennis? And do you mean the course machining marks in the bore of the brake when you say threaded interior?
Thanks
Joe
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The machining marks looked like threads... I prefer smooth...

Crowns left sharp sometimes need a bit of shooting to wear away a sharp 'edge'. They also are more easily damaged. I always finish my crowns with a piloted reamer that cuts a super smooth 60 degree chamfer. Been doing that for 50 years. The finish is smoother than anything lathe cut and polished.

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Cool thanks for the reply
Joe
guntech said:
The machining marks looked like threads... I prefer smooth...

Crowns left sharp sometimes need a bit of shooting to wear away a sharp 'edge'. They also are more easily damaged. I always finish my crowns with a piloted reamer that cuts a super smooth 60 degree chamfer. Been doing that for 50 years. The finish is smoother than anything lathe cut and polished.

60_degree_reamer.jpg
Titanium_700_crown.jpg
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Did the smith make the brake or just install it?
Had you had work done by this guy before?

If he made it, the workmanship kind of sucks. Not that it would really make much of a difference, if nothing actually touches the bullet, and both sides are the same, and it was on straight, but...The edge-on view of the brake appears to show that the slots were cut rather poorly. A straightedge will tell you in a hurry.

The threads on the barrel don't look like any great screaming shakes either.

Is the muzzle flat across the end or is it coned in like one of them 11 degree target crowns? While I respect Guntech's experience and solution to the crowns, and the tools he uses, there are enough good shooting results out there from other methods, that I would not figure that the issue unless there was some sign of damage or crookedness. Being protected by the brake helps to avoid some of the downsides of not recessing the crown.

Might be a good time to be considering doing some careful measurements of the chamber, and the concentricity of the fired cases, maybe a chamber cast and some time with a borescope, if you can, to see what the chamber actually looks like and how well it was cut.

Because, well, workmanship. As indicated by some chewy looking threads, burrs hanging all over the brake. The build quality of the brake looks pretty poor, if you have access to a lathe and milling machine, I figure you can do better.

Bedding checked? You have the capability of pulling the barrel off for a look at the threads?

Once all that has been given due consideration, if a barrel set back and recut chamber does not fix the problem, it's worth considering that the barrel is shooting as well as it is actually going to. Sometime a dud gets through.

Great pictures, by the way.
 
Markus, your crown looks chamfered to me. The pic as well as the tint from shooting made it look like it was flush. Your enlarged pic shows a very slight chamfer.

There is one other thing not mentioned here and it needs to be addressed. That is metal flowing from the hot gasses/residues passing through the brake and generated by burning propellant.

I have seen this on more than one occasion.

In your first set of pics, second one down, there is evidence of a build up on the inside edges at each stage of the brake. In your case it's likely powder residue but sometimes, if it isn't cleaned out carefully it can build up and be as hard or harder than steel. I have seen this build up lead to a condition where the bullet actually was passing AGAINST it, causing erratic patterns downrange.

That's another reason why the interiors of a brake should be polished.

Dennis suggests what IMHO is a rather large inside diameter for your brake but I can certainly see why.

A lot of people with brakes on their rifles don't CLEAN them PROPERLY. This is as important as cleaning the bore of the barrel properly.
 
bearhunter said:
Dennis suggests what IMHO is a rather large inside diameter for your brake but I can certainly see why.
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Good pick up... that was a typo I have since corrected .338 should have been .328 ... the bore of the brake needs to be 20 thou over bullet diameter if everything is concentric... so a .328" mandrel is needed...
 
That's one nasty looking, poorly machined, grotesquely dirty brake ya got there. I think that would be my first suspect. Try cleaning it first but I still think by the looks of the poor build quality that cleaning won't solve a thing. Try shooting without the brake or better yet, install a different one and try if you have another brake handy. Easiest place to start troubleshooting is with something that can easily be changed. A s#!tty, dirty, poorly machined brake will cause you more grief than enough.
 
I have yet to have a gun shoot worse with a properly made and installed brake. Some have shot better, some shot the same, but none have shot worse.
Precision Armament, Badger, are a couple of companies that make very good precision brakes.
 
I put the brake in my sonic cleaner and got it spotless. Tried shooting groups with and without the brake today.
No luck. Still 1.5" groups. Yet shot a sub 3" 5 Shot group at 300 M with my 270 and possibly a sub half inch group with my 243 at 100M. So.... I doubt it's me. I am going to swap stocks on it and see what happens. I have the original Remington LSS stock still and could also put it in my wildcat but don't like the idea of putting that much recoil into my wildcat stock. Should be ok if I keep the brake on though.
 
Markus said:
I put the brake in my sonic cleaner and got it spotless. Tried shooting groups with and without the brake today.
No luck. Still 1.5" groups. Yet shot a sub 3" 5 Shot group at 300 M with my 270 and possibly a sub half inch group with my 243 at 100M. So.... I doubt it's me. I am going to swap stocks on it and see what happens. I have the original Remington LSS stock still and could also put it in my wildcat but don't like the idea of putting that much recoil into my wildcat stock. Should be ok if I keep the brake on though.
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You're not flinching are you?
 
bearhunter said:
Markus, your crown looks chamfered to me. The pic as well as the tint from shooting made it look like it was flush. Your enlarged pic shows a very slight chamfer.

There is one other thing not mentioned here and it needs to be addressed. That is metal flowing from the hot gasses/residues passing through the brake and generated by burning propellant.

I have seen this on more than one occasion.

In your first set of pics, second one down, there is evidence of a build up on the inside edges at each stage of the brake. In your case it's likely powder residue but sometimes, if it isn't cleaned out carefully it can build up and be as hard or harder than steel. I have seen this build up lead to a condition where the bullet actually was passing AGAINST it, causing erratic patterns downrange.

That's another reason why the interiors of a brake should be polished.

Dennis suggests what IMHO is a rather large inside diameter for your brake but I can certainly see why.

A lot of people with brakes on their rifles don't CLEAN them PROPERLY. This is as important as cleaning the bore of the barrel properly.
Click to expand...

The crown appears to be a 11 degree target crown minus the 60 degree chamfer. I got the brake spotless in the sonic cleaner and the Smith removed the machine marks. Still no improvement today at the range. I will chase down bedding issues over the weekend and see how things go.
 
Maybe I missed it but how did the rifle shoot before the brake was installed???????? Even the best makers turn out a dud once in a while.
 
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