The primary ports of a muzzle brake are designed to direct gases horizontally (as opposed to vertically or aimlessly). The ports may not be horizontal when you attach them to a threaded barrel. To ensure that they are properly aligned, you’ll need a package of shims to time the brake.
Shims are pieces of metal that allow you to align a muzzle device correctly by filling any gaps between the two. You can find these in different thicknesses and sizes, sold in packages. Sometimes they have markings on them to determine the thickness.
Here are a few general tips:
1) Start by measuring the distance from the barrel’s crown to the front edge of the muzzle brake. This will give you a baseline measurement that you can use to compare against future measurements.
2) Use a shim of an appropriate thickness (depending on how much you need to adjust the alignment) and place it between the brake and barrel.
3) Screw the muzzle brake onto the barrel until it is tight.
4) Take another measurement from crown to brake edge and compare it to your baseline measurement. If necessary, add or remove shims until the two measurements match.
5) Once you’re satisfied with the alignment, you can secure the muzzle brake in place with set screws or thread locker.
Self-timing muzzle brake allows the user to install it and lock down the collar so it times on the barrel exactly the same way every time it’s installed.
The most detailed video for you to leave no doubt: