IIRC, H&R began using a nylon saddle in these models. Unload the revolver first. Remove the grips. Watch out for a small piece of white "plastic" (nylon) to fall out. Essentially, this is what locks into the single action sear. The revovers work just fine in double action but, they will either not lock into the single action or they simply will pull back and go forward when the thumb releases the hammer. This is DANGEROUS! The part should be replaced. It is not beyond DIY but, finding the part is. Numrich or Brownells could have the part.
