To remove the drum, do as was suggested and use the wrench flats if they exist.
If the drum doesn't have wrench flats on it, install a nipple in the drum.
Place an adjustable wrench (Crescent wrench) on the drum from the bottom of the barrel and tighten the jaws until they touch the drums outside diameter.
Align the jaws of the wrench and rotate it counterclockwise. One jaw will hit the nipple causing the entire drum to unscrew.
The flats on your 7/8" barrel are .362 wide.
That will allow the builder to use either the 1/4" or the 5/16 inch thread size for the drum.
IMO, a good builder would use the 5/16" size for the additional strength.
The threads will not be the 32 pitch threads used by the White Lightning and if the builder used the 5/16" threads there is not enough flat to rethread it to the 3/8 thread size so forget those liners.
The vent hole will line up good enough for a flintlock. They do not have to be located exactly in the theoretically correct place to work very nicely.
Yes you can use the existing lock screws but you are going to have to transfer their location to the new lock. You do this by installing the new lock and then using the existing (oversize) holes thru the stock to guide a drill that just clears the holes thru the wood.
With the drill in the stock and the lock installed, use an electric hand drill to lightly rotate the drill bit while it is in the stock screw hole, while pushing it against the new lock.
You want to create a very noticeable mark but you do not want to actually drill the hole into the lock.
With the hole locations on the lockplate established, use the correct tap drill to actually drill the holes thru the lockplate.
Some folks will advise doing this tap drill hole drilling thru the stock holes and if the best equipment you have is a hand drill that can help to keep the bit lined up but be advised, using the stocks existing holes can cause a slight mislocation of the newly drilled holes.
While I'm on a roll here, when you start to thread the holes it's a good idea to have the new lock installed in the stock and run the tap thru the bolt holes in the wood.
That will automatically align the tap.
The catch here is you do not want to fully tap the holes while the lock is installed in the stock. You only want to turn the tap into the locks holes about 1 1/2 to 2 turns. Then remove the tap. Also, remove the lock from the stock.
Tapping requires the use of a special threading oil to keep the tap from breaking. This rather stinky oil has sulfur added to prevent the tap from welding itself to the steel as the threads are being formed.
Thread cutting oil is available at almost any hardware store and it's cheap. Don't skimp and try to use regular motor oil. If you do, you will break the tap.
To start the threading, with the lock removed from the stock, apply the cutting oil to the tap and to the hole.
Gently turn the tap into the partial threads you started a moment ago allowing the partial threads to guide the tap. When it starts to resist after going in 1 1/2 to 2 turns use the tap driver to turn the tap into the hole.
Taps are very hard and very brittle. If you try to force it to go where it doesn't want to go it will break.
When tapping you must stop every turn to turn and a half and back out the tap at least 1/2 of a full turn. This will break the chips that have been formed.
After backing the tap out 1/2 turn, run it in until you feel resistance. Then apply a little more torque to run the tap in another turn to turn and a half. Then repeat the backing it out.
Keep this up until the tap screws easily completely thru the lockplate.
If you allow the tap to go where it wants to go and you apply just enough pressure to turn it in and you back it out to break the chips you will soon have a correctly hole so if the lock has two lockscrews repeat this on the other hole.
You will need to shorten your new vent liner. I've posted several times how to do this but it involves using a hex nut, a pair of locking pliers and a flat file.
Have fun.
