Drilling the rear lock bolt:
Basically we have it all still set up from the front hole, & marked & etc.
1: I lay a straight edge across the tang of the rifle looking from the top & I draw a line from rear sideplate hole mark to rear lockplate hole mark, that I have previously marked for the lockplate bolt.
If it is at a slight angle I then mark the bolster where I want the screw to go & centerpunch it & drill thru it with a 3/31" drill bit, and slightly at the appropriate angle if necessary. The bolt is supposed to be straight across but once in a while it doesn't turn out that way. This is why it is Most Important to use a pilot hole & also to tap the bolts thru the rifle, as this way you are sure of bolt alignment with threads.
2: I now put a small "C" clamp on top of the breech of the barrel & down to the trigger area to insure the tang doesn't lift & make sure the breech stays in the stock. Now I drill the hole for the lockbolt with the appropriate size hole for the 10-32 screw THREADS, drilling through the sideplate, thru the tang and stop, all of this using a drill point attachment on the drill press.
3: I stop 1/2 way thru the tang & turn it over & drill from the lock bolster side. The reason I do this as when I drill thru the tang sometimes it has hit the tang at a slight angle & it is possible the bit has wandered off center just a tad... thus I will drill thru the other side & see how the holes match up & they will be close if not perfectly in line.
4: If the holes don't meet exactly, DO NOT work the bit through the bolster of the lock as you will egg shape the hole you need to thread. You should be very close if you used the drill point & good sharp bits, as it takes little pressure to drill this. If you use dull bits & lots of pressure, that is where ya get into trouble.
5: Now change bits & drill for the shaft of the 10-32 screw from the sideplate to the lock with a Drill Stop on the shaft of the drill, stopping it 1/8" of the lock bolster.
6: Remove the drill & tap the 10/32 hole through the sideplate, stock, tang & thru the bolster. Now we know we have bolt allignment, even if slightly at an angle, we know it will go thru.
7: Take out the tap, drill the same hole from the sideplate to through the stock, tang, up TO 1/8" of the lock again (using a drill stop) with a 1/32" larger sized drill than the 10-32 bolt shaft. This will give you clearance & remove all possibility of any stress on the lock bolt & lock inlet from recoil from the rifle thru the tang hole.
8: Now we have both bolts drilled & clearance of the bolts & they are all threaded in, but we have excess threads. Run them all the way in & take a permanentt marker & mark the threads, take the screws out & cut off the appropriate amount, file smooth & refit them. It is important the front lock bolt not go past flush with the face of the lock as if it does it will push the frizzen spring out & possibly break it. The rear screw should not go past flush either & interfere with the cock.
Tang Bolt to Triggerplate:
1: Basically, the trigger to tang bolt is the done the same. Inlet the trigger appropriately & retain with the rear screw in triggerplate & small "C" clamp on front of triggerplate (the best ya can), mark & centerpunch the holes, drill the pilot holes. (NOTE: I must mention this hole will most likely be at an angle & a pilot hole here is a Must}
2: Drill the thread size holes all the way through, using a drill point attachment on a drill press..
3: Tap the triggerguard hole gpoing down through the tang to the triggerguard.
4: Drill a 10/32 shaft hole down through the tang & stock & using a drill stop to insure you stop before drilling the triggerplate.
5: Countersink the tang the appropriate depth for the type of screw you are using.
6: Insert screw & mark the excess with a permanent marker, remove trim & refit. The screw in this plate is to be flush with the exterior of the triggerplate.
I hope I didn't miss anything...If I did please someone chime in.....
Custom Muzzleloaders & Custom Skinning Knives 
