Why on earth would you want to put your thumb into the BCG? You can exert more force with the forward assist....and not get covered in crud while doing it.
Springfield Armory M1A 22" barrel in SAGE EBR Mod 0 stock
Dan Wesson CCO | S&W Model 58 blued | S&W Model 29 blued
Springfield 1954 M1 Garand | S&W M&P 15 VTAC 2