Witt Machine was at the range showing off their assortment of muzzle devices. The most eye catching was this shoulder cannon. I was told that even though they strapped the cannon down with some robust heavy duty straps, it ripped through 5 of them due to the muzzle climb when they shot it remotely with a string. They used 3/4 lbs of powder.

Here is a clamp on muzzle brake that he made. It is for a cannon.

Here is a video of the muzzle brake in action.