NM converted to a 4 click OM action w/o transfer bar or loading gate lockouts using OM hammer:
The OM hammer is almost a drop in, and the trigger needs simple modification:
Remove the transfer bar. The loading gate will be freed up so you can open it with the hammer in any position or cock the hammer with loading gate open.
1. Shim the hammer screw hole, because the OM screw is slightly larger than the NM pin. And that's simple: take a 22 case with bullet and powder removed and primer fired which is just the right size, (a fired 22 shell won't work because it's expanded), press it into the OM hammer screw hole in a vise, and cut the case off flush on both sides. Debur the edges and clean out with a 22 bore brush. Now the NM hammer pin will fit perfectly.
2. See the NM trigger on the right in photo below: Cut off the transfer bar connecting boss from the trigger to clear the OM hammer base.
3. The very thick Ruger NM trigger sear must be thinned down from the front side (to the shape of an old model Ruger trigger shown on the left, below) to fit the OM hammer notches. The rear corner of the trigger, which is the actual sear is not touched, so sear geometry for proper full cock is not affected.
_______________________Clements two adapter triggers are shown in the center_________________________
OM trigger__________________standard____&____Bisley w/over travel stop__________________NM Bisley
OPTION 2:
You can also purchase the Power Custom "Registered hammer", http://powercustom.com/store/index.php?main_page=product_info&cPath=12&products_id=1119
You will not need to cut off the trigger transfer bar boss but still need to thin the trigger sear (or buy PC's already thinned trigger).
OPTION 3 for a 4 click Bisley hammer:
You can also purchase the PC "Bisley hammer for old models", http://powercustom.com/store/index.php?main_page=index&cPath=12&sort=20a&page=3
You will need to make all modifications above, shim the screw hole, cut off the trigger transfer bar boss, and thin the trigger sear (or buy PC's already thinned trigger and just cutoff TB boss).
If you don't have a Bisley grip frame, you'll also need to reduce the hump on the back of the Bisley hammer.