I have made up some muzzle adapters for the GSG 522 platform. These thread into the triple tree and slip over your barrel to give you 1/2”-28 threads. They are black nitride coated. Wrench flats let you tighten them up. These were copied from a sample manufactured by a different company with some slight changes.

With the proper Form 1 you can cut your barrel back to 0.865”, measured from the edge of the triple tree to the edge of the barrel(see pic). This should allow the correct interference between the barrel and the adapter. YOU are responsible for correct fitment and ensuring this centers your barrel correctly!

These are $75 each plus the ride. PP F&F preferred or you pay fees. I imagine shipping will be about $10. If it’s over that I’ll eat the rest.