For the Smith knowledgeable out there. A while back I picked up a 6906 in great shape. It's got the bobbed hammer with grooves on top to aid in manually cocking the hammer if so desired. Works great. I came across a 4013TSW a couple days ago also with a bobbed hammer but the hammer is smooth on top. Question is can a gunsmith acquire a conventional spurred hammer (as used on other s&w 3rd gens) or a bobbed hammer with grooves and replace the smooth hammer on the afore mentioned 4013?