How important is it to have the muzzle brake concentric to the bore from an accuracy point of view?
Mostly in terms of the outside diameter.
Mostly in terms of the outside diameter.
Gunsmithing Muzzle Brake Concentricity
- Thread starter ShtrRdy
- Start date
Outside diameter not so much. Inside can affect accuracy and bullet stability. Especially if you get a "strike".
The bore is run concentric then muzzle machined. Seems like much ado about nothing but it is important. A brake, flash hider, can , etc MAY change the point of impact to a degree but the change will be consistant if done properly. In most cases the change of impact is non existant if done right.
Ditto's to the above.
Did you recently have a muzzle brake installed on your rifle? If so know this. Most factory rifle barrels are not concentric so when muzzle brakes are being installed sometimes there can be a slight edge/ledge that can be hard for some guys to make disappear.
Pull your bolt out. Take a cleaning rod and rub some El Marko marker on it. Run the rod back and forth like you are cleaning the bore. Not more than four or five times. If the marker is is rubbed off or there are parallel lines on the rod get it checked by a professional.
Make Lady Luck your friend; not your partner.
Did you recently have a muzzle brake installed on your rifle? If so know this. Most factory rifle barrels are not concentric so when muzzle brakes are being installed sometimes there can be a slight edge/ledge that can be hard for some guys to make disappear.
Pull your bolt out. Take a cleaning rod and rub some El Marko marker on it. Run the rod back and forth like you are cleaning the bore. Not more than four or five times. If the marker is is rubbed off or there are parallel lines on the rod get it checked by a professional.
Make Lady Luck your friend; not your partner.
If I understand you correctly, the bore in a good rifle barrel is concentric when the barrel is installed on the receiver. Then if threads are cut on the muzzle end of the barrel, they may not end up concentric with the bore?
I figured the addition of a brake, flash hider, can, would move the POI - because of the extra weight on the end of the barrel slightly bending the barrel down?
Thanks, Todd
If the marked up cleaning rod has the marker rubbed off or parallel lines, what does this mean? What are we looking for?
Thanks, Todd
My understanding of this is that rifle drills will wander slightly as they are boring a blank. The beginning and end may be concentric on the blank as it comes from the factory, but the bore will trace an ever-so-slight arc through the cylinder of the blank. When you trim the blank to your final dimensions, the bore may have some runout with respect to the OD of the barrel. By indicating off the bore itself, either with range-rods or directly with a long-reach DTI, you ensure that the bore is concentric with your lathe spindle and that's the measurement that matters when threading for a brake. You do this in two places: the very end of the muzzle and 2 inches or so into the bore to ensure that that last couple of inches that the bullet sees are straight and true.
The rod is only a quick field test. If it's marked up take it to a gunsmith who can check to make sure you have the proper alignment. It can be fixed if it isn't aligned. You could open up the inside diameter of the brake which won't really make a different with the overall performance of the brake. The other is simply cutting off the current threads and rethreading the barrel.
I agree with this. It comes down to the tennon which is to be threaded needs to be concentric with the bore.
Presently I am using a range rod/bushing with a couple of .0001" indicators setup. It may not be the best but it's all I have for now.
In my opinion it is very important that the muzzle brake be concentric with the bore, both the inside and outside.
The bullet exits the brake before it can have any real effect on it unless it strikes the brake and then it destroys
accuracy and can be dangerous.
I have seen brakes that were installed by threading the barrel tenon with a die nut. these gave real problems.
Brakes normally have .010 thousandths clearance on each side of the bullet so any misalignment can cause
bullet strikes if not installed correctly.
Hope this helps
J E CUSTOM
You thread the muzzle concentric to the bore. If the outer diameter is off, after threading, shouldering, crowning, etc. You then rezero the outer diameter to finish a clean installation with the brake installed.
Normally after the bore center line is established and the threads are cut for the brake with the shoulder to seat the brake, the OD of the barrel
is only a few thousandths off (.002 to .007) you cant see it and you would have to re-contour the whole barrel to make it true and look right.
If a barrel has more than .005 Total Indicated Run out I don't use it.
So the outside of the barrel is not an issue for brake installation if it is not bad. And as long as you cut the threads true/concentric to the bore(
very important)It will be fine.
I don't like any outside out of concentric with the bore condition but will except a few thousandths because it happens with factory barrels.
Good custom barrels seldom have any run-out.
J E CUSTOM
Why did you revive an 11 year old thread with a quote?? 
