Witt Machine & Tool made a cannon muzzle brake. Shown next to my business card for a size comparison.
From the guy I spoke with at Witt, this gave them an idea to turn a Mosin-Nagant into a canon. This is used with three quarter pounds of powder and it is secured to a platform for firing.
Maybe next year we will see a version with its own muzzle brake attached.
Witt Machine Official Site | YouTube