The Boberg XR9-L fits a service-length barrel into a subcompact pistol by using a peculiar rotating-breech barrel lock and claw feeding system that makes room for the gun’s 4.2-inch barrel.
It’s rated for +P and performs outstandingly with it. Compared to my Beretta Nano, it’s capable of generating almost 200 foot-pounds more energy down-range, at just under 500 foot-pounds, or about 60% more power.
The only real drawback to the Boberg is the price. They start at $1,050.
Still, weighing in at just 18.5 ounces and having a capacity of 7+1 rounds of ammo, if you can afford it, it’s hard to find something that has more power in a package that size.