Question about the two piece barrel

[JackP]

According to the drawing in the Nicolaus book there are grooves in the barrel both on the rear and forward ends of the gas cylinder. There is no indication that the gas cylinder is crimped into the rear groove. Perhaps it only serves to locate the rear surface of the gas cylinder. The detail in the drawing is not clear but it suggests there is also a short section of the barrel next to the forward groove that is of an unspecified larger diameter than the rest of the barrel . I believe this establishes the forward locating surface for the gas cylinder. The rear groove is .12 wide, the front groove is .18 wide and may be tapered to match the shape of the crimp. It looks like the cylinder is only crimped in the front.