Respectfully ... Back to first post and problem. Those pesky OEM type taper pins can be very difficult. The key to success is setting up the "smack" and using the correct tools and procedures. No big deal. Fun and easy if you take the time. You might have a situation where the manufactures did not pay attention to specs. Happens nowadays. SPECIFICALLY: The barrel taper pin grooves have a OEM taper. Lots of time today that little procedure is done away with? Hardwood backing will not work. Too compressive. Has too much rebound. Also a concrete floor doe not work. Also rebounds. You need a steel anvil or an anvil surface on that big necessary 5-6 inch through-bolted on vise. Then steel plates and shims to properly align the site base on the smacker. Steel underneath. Wood blocks needed to properly align the upper or barrel. Use bungie cords to lock down the barrel. Exact alignment needed here. Find and use a proper sized steel drift. A straight pin punch is best sized to smack that smaller diameter end OEM taper pin. Use vice grips to hold the punch. Then hold the vice grips. A big hammer is good. 3 pound best. Patience. Consider Marvels Mystery Oil soaking for hours. Overnight better. Let the oil do the work. You have rust welded stuff. Or BAD manufacturing. Then once all set up correctly, take a big smack with that big hammer. WACK! Irresistible forces meets the movable object. Have Fun. Enjoy doing this. You can do it. Hundreds of builds. EDIT EDIT EDIT You might have a taper pin manufacturing problem. You taper pins MUST have a small end and a big end. MUST! Straight diameter pins are shieeeet. Drive from the small end. Your taper pins MAY have been installed incorrectly.