But, if you're just replacing your factory steel pistol barrel with this one, you don't have to fill out anything. I almost did just that, until I disassembled my pistol and weighed the steel barrel. It weighs 13.75oz...this one weighs 11oz. I decided not to spend 300+ to save 2.75oz, but that's just me...YMMV, lol!
This would turn your m&p 15-22 rifle into a nfa regulated short-barreled rifle. This requires registration with the atf and a $200 tax stamp.
The firearm pictured is the factory built M&P 15-22 Pistol configuration with a pistol brace, and the barrel shown is for the pistol version. Adding the short barrel to your factory 16” rifle will make it a SBR and will have to be registered on a Form-1 or the FedBois will get angry