21. The rifle has a rotating bolt head with three lugs, which combine to provide an effective locking surface. 22. Cartridge / calibre changes can be accomplished by the change of a bolt head or complete bolt assembly. 23. It has a three-way selector between single, automatic fire, and milled parts were the barrel and the bolt head . 24. Friction in the threads and under the nut or bolt head use up some fraction of the applied torque. 25. Matching the nut shape to the shape of the bolt head is more a matter of esthetics than function. 26. This version had a new bolt head , an improved firing mechanism, modifications to the chambering, and a new rear sight. 27. The weapon features a semi-rigid two-piece bolt mechanism that consists of a bolt head and a supporting angular locking piece. 28. The bolt head is rotated by a control cam riding in a helical guide slot machined into the bolt carrier. 29. The blowback action Oerlikon SSG36 has a deep chamber in which the cartridge totally sinks along with the bolt head . 30. The bolt construction is significantly revised, allowing removal of the bolt head from the bolt body with simple hand tools.
