muzzle brake accuracy went boom!

C

Chet

Guest
I installed a muzzle brake on my 300 win mag. and accuracy went south, from around 7/8" at 200yds to 2" plus. clearance hole at where bullet exits is approx.plus .018-.020, but the web thickness at the end of the brake is approx 1/4" should this be a thinner web, the brake is about 2" long with a series of 9/32 dia holes, I really never heard a brake deteriorating accuracy. any tips to correct this problem.

Chet
 
Does it still shoot okay with the brake off? If it is does then:

Make an accurate mandrel about 4 inches long... one half of this to be turned so it just slip fits in the bore of the rifle freely. Pointed upwards you should be able to shake it out of the barrel... then turn the other half to a diameter of .325". Your brake should have a true hole in it of .328" - .330". With the brake in place and the rifle pointed up, you should be able to freely shake this mandrel up and down. It should not bind. If it does there is something out of line...

do this with an unloaded rifle... :D

It may require a different load due to changed harmonics.
 
Muzzle Brake

If a muzzle brake is tightened too much it will cause some constriction to the bore and can be very detrimental to accuracy. If the threads are relatively small compared to the bore size, for example 1/2" threads on a .30 caliber, it does not take a lot of torque to cause this. The solution is to only snug up the brake gently. It is better to use locktite and have it stay on permanantly than to have it come loose, which will also hurt accuracy.


Scott Roeder
 
How was the brake made and installed?

I always finish bore and ream the brake AFTER threading the barrel and screwing the brake on the barrel. The thread on the barrel is made concentric with the bore. That insures that there is equal clearance around the bullet after it exits the barrel. The final step is to finish the o.d. of the brake. The outside of the barrel is usually not concentric with the bore meaning the barrel I.D. and O.D. must be dialed in seperately.
Your bullet may be clearing the brake bore by .001 or .002 on one side and .015 to .017 on the other side. Uneven muzzle blast may be influencing the bullet's path.
Just a wild guess as to a possible cause on affect on accuracy. Maybe I'll put one on way off-center sometime to see if there is an affect.

Jay, Idaho
 
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I've never seen it make that much difference- either your crown is toast or something is crooked.
 
brakes

What Jay said is exactly correct.....bore and o.d of barrel are 2 seperate set-ups.....with respect to the brake install.
 
I just got back from he shop, the hole measures .330 and it is concentric with the bore, I made a step pin, .301 dia x .327 and there are no issues with clearance, it is concentric, when I made the brake, I set up the barrel with a pilot and I indicated it in both ways to be concentric with the bore and ran the indicator down the pin about 1 1/2" and adjusted the rear spider accordingly, then I already had a 1/4 hole in the end of the brake, I installed it and bored it out, it is dead nuts. maybe it is me, just not used to shooting this rifle I had stored for 3 yrs, coming off of a 6bR maybe I need to get the hang of these larger calibers again. I hope it's me but I will shoot it again to make certain!


chet
 
Do you have any.........

baffles in the brake?? That might help you to break up the gas getting ahead of the bullet before enough escapes the sides. Look at the brake for the M1-A by Smith Enterprise, its very effective and doesn't hamper the accuracy.;)
 
In my experience adding a break almost always affects accuracy even in small ways because you have added weight to the barrel, I tell everyone to expect to have to change their load to accommodate this, so far it has always worked out. I always re crown my barrels after threading as well. I don't think breaks will make a gun more accurate (with the exception of adjustable breaks which can be dialed in) but they can make the gun more fun to shot and you will get more practices and learn the gun.
 
Do you REALLY want to take............

a nice muzzell, and then "Break" it? Why would anyone want to break a perfectly good barrelle. I've seen too many breaken barells to ever do that again!!;)
 
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Muzzle Brake Installation

Jay,

How much distance do you leave between the end of the muzzle and the back end of the inside of the muzzle brake?

Bob
 
Bob,

I don't have a "standard" for that, just insure that there is more female thread than male so that I don't get a C buildup on the male threads that would cause problems during removal.
Most of my brakes are on Varmint or HV barrels and are similar to the original Vais brakes. There is an undercut ahead of the female threads of about 1/8" wide and large enough to allow the longitudinal holes to be fully exposed. These seem to work very well and are installed prior to barrel break-in and load work.
I have made a number of "thread protectors" that weigh the exact same as the brakes so that when brakes are removed to meet rules and replaced with the "protectors", accuracy is not affected. This was popular when PA/MT did not allow brakes in Heavy Class. A lot of shooters shot their Light guns in Heavy. That is no longer an issue.

Jay
 
here is something that happened to me...started with a nesika/krieger/lone wolf tactical. 300 win with a vias and leupold MK 4. it was one of the most accurate rifles i've ever fired and then it went to hell. checked and measured EVERYTHING and found the baffle to bore tolerance had tightened up to only .008" over bore diameter (started @ .030" over). it appeared that the brake was reamed from the muzzle towards the breach and there was a small burr left on the front of each baffle that rolled into the path of bullet and caused an uneven issue around the bullet path. 60 rounds of trial and error later led to the bore being honed out and the accuracy going right back to awesome.
too close of a brake baffle to bore diameter can lead to issues as well as uneven baffle bore diameter. hope my past issues help your issues.
greg
 
Installed my first MB on a savage F-Class 6.5-284. Before installation, it was grouping 14 in @ 1000 yds. After installation, it shot under 8 in ( 10 shots ) at 1000 yds. with the exact same load. My take on it is it changed the harmonics or barrel shock wave. I took great care to insure the bore of the MB was within .0005 concentric with the axis of the muzzle.

Ed.
 
I once had a Browning stainless stalker in .300 win mag that was a good shooter, I could depend upon three shots into 1/2 inch out of a cold barrel using Federal premium 180 grain loads.

I sent it off to Magnaport and it came back shooting just the same, except for the reduced recoil and a bit more noise. The EDM process slightly lightened the last few inches of the barrel, but apparently not enough to throw it's shooting characteristics off.

Encouraged by this, I went ahead a replaced the tire-rubber recoil pad with a 'decelerator' pad, and the gun ended up being quite pleasant to shoot.

Like a fool, I traded it off not much later for a shotgun that caught my fancy... Never swap off a gun that consistently shoots well for you.

Kind Regards, CharlesB
 
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