Home Forums Hunting & Shooting AR and Tactical Rifles Tac 20 build (pic heavy)

Got started on the barrel, and will be reaming the chamber tonight or tomorrow.

Truing up the barrel with a fitted bore rod. This required turning a tool steel rod to .1993" to fit the bore in this barrel. The barrel is held only by the first tooth of the chuck jaws (blank is oversized so I turned a locating ring that is centered to the bore), and located at the rear with a spider. This allows me to adjust the angle of the barrel in the chuck to align the bore. Usually this is done with a 4-jaw chuck, but I got lucky with this very well zeroed 3-jaw. I adjusted the spider until neither indicator needle moves when rotating the chuck.


Located at the rear by a spider:


Facing the blank:


Chamber end of the barrel is ready to thread. The section to be threaded is .810" OD x .620" deep, and will be threaded 16 TPI to match the barrel extension.
That second step sticking out of the chuck is the 1" OD the barrel will be at the chamber end before tapering or stepping down the profile. Lots of material to remove from this 1.25" blank!


This pic shows the raised ring in the blank where the first tooth of the chuck jaws grip:


This is a different barrel, a pre-chambered BHW blank in 243 LBC, but it shows what the 20 Tac chamber end will look like after machining, before the barrel extension is attached.