Muzzle Crown

[avcrew]

Changed out a few muzzle devices in some long guns and noticed how much crud builds up on the crown of the muzzle.

Question is, how much does the original muzzle crown matter if a muzzle brake is attached?

If a muzzle brake is installed, is it the crown of the brake that matters?

[ar15barrels]

The end of the rifling/grooves is what matters.
Carbon builds up, but is generally self-limiting in that every shot wipes off the excess carbon from the last shot.
Some muzzle brakes are very restrictive in gas flow at the crown and will actually build up enough to effect accuracy.
If you are having accuracy problems, cleaning out all the carbon is an easy test to do with some Slip2000 Karbon Kutter.

[avcrew]

Some muzzle brakes are very restrictive in gas flow at the crown and will actually build up enough to effect accuracy.

I went from crush washers to shims. I noticed that crush washers, because they are thicker allow a greater gap between the barrel crown and the internal stop of the brake. Shims, however, get the brake much closer to the crown. Which is preferred?

[theLBC]

what matters more (i believe) is the last contact the bullet has with the barrel.
that said, the muzzle device can affect poi depending on how it is designed.

[ar15barrels]

I went from crush washers to shims. I noticed that crush washers, because they are thicker allow a greater gap between the barrel crown and the internal stop of the brake. Shims, however, get the brake much closer to the crown. Which is preferred?

You want as much clearance in front of the crown as possible.
Ideally, you should be able to look sideways into the muzzle device and see the exposed crown.
With access like that, you have room for the gas to escape freely and excess carbon will not build up.
The worst designs have a small bullet hole in the muzzle device just forward of the threads which creates a cavity which eventually fills with carbon because the gas can not escape to the atmosphere at a 30 to 60 degree angle from the bore.

[avcrew]

Using a VG6 Gamma brake.

The muzzle crown is quite visible from the side holes of the brake and is not obstructed. In fact the rear exit hole of the brake is quite open and the forward holes get smaller as a bullet exits.

I'll be sticking with shims for these brakes.

Thanks.