Gunsmithing Muzzel brake errors

[goober]

I recently fitted a muzzle brake to my 32" barrel which is throated for my 284 shehane round launching a 180gr Berger projectile . The rifle "use" to be able to shoot 1/4 inch or better if only I could but since fitting the brake whooaahh 3/4 inch and no set pattern .
The brake is made here so a non branded brake but looks well made and doesn't have strike.The brake has 4 ports per side plus 3 on top .

I am going to have the crown checked but it looks ok .My questioned probably is can the harmonics change so much as to do this because when I take the brake of it tightens up but not as good as it once was .
I am perplexed

 

[bohem]

Re: Muzzel brake errors

Take the brake off and reshoot.

The brake might be installed crooked and without it on there the groups are back to OK.

If the groups are boned with the brake off you may have a crown issue as well or instead of a brake issue.

 

[Hellbender]

Re: Muzzel brake errors

If the bore is not absolutely concentric with the bore of the brake, sometimes you can open the hole in the brake another .010-.015" and fix the problem.

If the smith that threaded the barrel didn't index it properly, he may have messed not only the threads up, but if he re-crowned it, it could be off as well.

 

[Mutt]

Re: Muzzel brake errors

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: ch'e</div><div class="ubbcode-body">I recently fitted a muzzle brake to my 32" barrel which is throated for my 284 shehane round launching a 180gr Berger projectile . The rifle "use" to be able to shoot 1/4 inch or better if only I could but since fitting the brake whooaahh 3/4 inch and no set pattern .
The brake is made here so a non branded brake but looks well made and doesn't have strike.The brake has 4 ports per side plus 3 on top .

I am going to have the crown checked but it looks ok .My questioned probably is <span style="font-weight: bold"><span style="text-decoration: underline">can the harmonics change so much as to do this</span></span> because when I take the brake of it tightens up but not as good as it once was .
I am perplexed </div></div>

Short answer: YES!

Often the change in harmonics is enough to necessitate finding that sweet shooting node once again (assuming of course you're shooting handloads). For some the shift/change is A LOT. For others, not too much. Then the lucky few that have none. Heck, Tubb even sells a tunable brake to counter the affect.
Pulling the brake <span style="font-style: italic">~should~</span> bring back the previous POI and behavior.
Why it doesn't come back to original groups size is curious to me, though. Disturbed from threading? Nicked crown? Placebo effect?

Good luck!

 

[Pete Lincoln]

Re: Muzzel brake errors

open up the bore of the brake and i bet the problem disapears.

 

[Keith Johns]

Re: Muzzel brake errors

Most say to go .020" over for brakes.


What is the most a guy can go over before losing efficiency with the brake?
Is there a cut off point?

If you open a .243 brake up to .300, how well will it work? I realize brake design matters, so lets say its a Bradger Thruster. Anyone opened a Badger thruster up to like .040" over bore size?

Thanks

 

[Dollman]

Re: Muzzel brake errors

The brake on my .260 Rem rifle is 0.315" in inside diameter and my .300 Win. Mag. brake has an inside diameter of 0.375" if that will help. Elite Iron makes the brakes and they are the Max Tac versions. They both work extremely well. Especially the one for the .300 Win. Mag.

The top picture

http://eliteiron.net/elite-iron-MuzzleBrakes.html

 

[Field]

Re: Muzzel brake errors

I don't think you would be able to tell the difference between .20 and .40.

 

[mcfred]

Re: Muzzel brake errors

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: ch'e</div><div class="ubbcode-body">...when I take the brake of it tightens up but not as good as it once was.</div></div>

Well, the gun must have been taken apart to install the brake, so I'd check that there is nothing pinched between the action and stock, various screws are tight, etc. It seems like with the brake removed it should be as before. What was the original OD of the muzzle and what is it now? A button rifled bore will expand very slightly if enough material is cut off the OD. Hammer forged barrels will constrict slightly.

 

[Dollman]

Re: Muzzel brake errors

I've been told not to remove the brake from my rifle for when I clean it. I've also been told over tightening it can distort the last inch or so of the barrel... permantely. I don't know if this is really true or not. But, I do remove the brake to clean the carbon build up off of the crown after every 100 or so rounds. Brakes usually cause terrible build up of carbon on a perfectly good crown. At least thats my experience. When I replace it I just snug it and so far it has always returned to where it was originally at. If it is true that overtighting can ruin a barrel I havn't screwed up the end of my barrel yet.

 

[LRI]

Re: Muzzel brake errors

Opinionated Chad here. Get your salt. . .

I call bullchit on harmonics.

If I'm wrong then there's a simple solution. Change the load. It should/will improve.

I've installed hundreds of brakes. Some work, some work better.

Radial and symmetrical ports seem to work the best.

Brakes with holes on top/sides should be avoided IMO.

Case in point. In 93 the AMU went to the M-16 and they cleaned house at Perry. Tore the Marines a new one that year.

Following year PWS built M-16s fitted with compensators. Guns were fine on the short course but had elevation at 600.

Why?

Look at a comp and its pretty obvious. Ports on top/sides. It induces a yaw on the ass of the bullet upon exit of the crown.

2004-2005: I was part of the design team for the Dakota Arms Scimitar built for the Jordanian military. 308 and 338LM mag fed bolt guns for use againts militant Islamists.

My boss made a brake with non symmetrical ports against my recommendation. Guess what? History repeated itself. I made a symmetrical brake of same length/weight as his.

Groups improved even more~likely due to the gun being easier on the chooter.


Experience from 20+ years at this (in one capacity or another) tells me its NOT due to fancy words that get used way too much on gun forums.

Opinion over. Light your torches and fire the ovens.

Happy Saturday Germs.

C.


PS:

If it were me id first ensure the brake is tight. Assuming it doesn't have non symmtrical ports I would pull the stick, indicate the bore in the lathe, install the brake and check TIR. It should be zero. If its not then bore the id till it is.

If it is be sure to check TIR in two places to ensure its on the same vector as the bore. If its not, bore till it is.

Leave the drills in the tool chest. Single point boring bars are what you want as they cut a clean hole on spindle center. Drills just make holes w/runout bigger.

If this still doesn't work, sacrafice a puppy and make a deal with the devil cause your just screwed.

Kidding on the last part. Use a cat!

 

[goober]

Re: Muzzel brake errors

Thanks guys for some solid advice!

 

[THUNDERBOLT68]

Re: Muzzel brake errors

Jp brakes have holes in top, In my opinion are the best brake out there.

 

[2156SMK]

Re: Muzzel brake errors

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Keith at PCR</div><div class="ubbcode-body">Most say to go .020" over for brakes.


What is the most a guy can go over before losing efficiency with the brake?
Is there a cut off point?

If you open a .243 brake up to .300, how well will it work? I realize brake design matters, so lets say its a Bradger Thruster. Anyone opened a Badger thruster up to like .040" over bore size?

Thanks </div></div>

It won't matter.
Standard practice in suppressors is 1mm over bullet diameter.
Suppressor makers fret more about efficiency than muzzle brake makers.

I go 0.030" over as my standard practice.
I would challenge you to try and feel the difference between 0.020" and even 0.060" over.
It's just not gonna matter enough to notice.

Having said that, I would not go 0.200" over and expect it to work as good as 0.030" to 0.040" does.