G.I. Contour; Threaded & Short-Chambered
Standard G.I. contour barrels are machined from 4150 chrome-moly steel and fully threaded, with button-cut 4-groove rifling and a durable, Parkerized exterior finish. M1 Garand barrel has a 1-10" twist rate, and M14/M1A barrel has a National Match, 1-12" twist rate. Both come short-chambered—after installation, complete the chamber with a finish reamer until correct headspace is achieved.
Big Book Catalog, Issue:66, Page:168
SPECS: 4150 chrome-moly steel, Parkerized, matte black finish. Not chrome lined. M1 Garand - 1-10” twist rate. 24” long. .30-06. M14/M1A - 1-12” twist rate. 22” long. .308/7.62mm.