No drilling or tapping is necessary as the steel base clamps directly to the barrel. See-through design allows you to use your iron sights even with a scope installed. Please note that this base was designed for use with the stock Ruger barrel only, it will not work with heavy aftermarket barrels. Notes: See through design allows use of open sights.Clamps on to the barrel.Stock barrel only. Will not work with aftermarket heavy barrels.Install by removing the top section of the gas block. It is held on with 4 cap screws. Install the scope base with the rail section facing to the rear and attach it to the bottom section of the gas block with the 4 cap screws.This is a scout-type scope base, mounting the scope forward of the action.