When I got my .270 Win BLR in January of this year I too thought about adding a hammer extension and looked into it a bit. As I recall there are two different BLR hammer extensions - one for for pre-1992 models and one for 1992 and later models. I decided against adding a hammer extension as medium height Leupold rings on Millett BLR bases with a Vortex 3-9x40 scope afforded sufficient thumb clearence to safely manipulate the hammer.
