The L shaped recoil lugs were only used in the pre-Mk13, Mk13 Mod 0, Mk13 Mod 1, Mk13 Mod 3, and a few old and obscure SEAL sniper rifles and target rifle from the 1980’s.
The Mk13 Mod 2, Mk13 Mod 5, Mk13 Mod 6, and Mk13 .7.62x51mm training rifles all used the .25" straight profile (no taper)...