Drum install issue

[stuckball]

Good day folks.  This is my first post, and I need advice before I screw something up.  I am continuing a build that I began probably 20 years ago.  It is a Southern Mountain Rifle that was bought from Pecatonica River.  The stock is pre-carved for the lock.  I am ready to install the drum on the barrel in the center of the flat.  However, the lock cut-out is too shallow for the drum to center.  Is the fix for this to file the cut-out deeper.  It looks like it needs about 1/32 -1/16” more room for the drum to fit.  I was just going to use a rat tail file.  What do you think?

[Daryl]

Yes.  You need to fit it perfectly, so the lock plate supports the drum.

[Gaeckle]

Use inletting black on the drum, that will help. If the inletting black is not perfectly showing on the plate, use a C clamp to mimic the tang bolt you see if that improves the imprint.

[B.Habermehl]

My way to fit a percussion lock and drum. Determine exactly where the breech plug face is inside the barrel, layit out on the outside scribe a reference line. Check this relationship with your lock plate. Completely inlet barrel and tang. In your case you will need also to inlet the lock. I normally take some .010 shim stock and shim the tang up a bit. Now do your drum fitting lay out center punch drill and tap. The purpose of the shim is to be certain you have good support of the powder drum. It is removed after all fitting is done. When cleaning the gun the tang bolt must be loosened to remove the lock. Just my two cents. Fileing the lock bolster is sometimes necessary to allow the drum to center on the barrel flat. Just make sure you don’t need to go so far as to mess up the relationship between the hammer and nipple. All said and done I’d personally rather have a flint lock🙃

[Bob Roller]

Once in a while I made locks with a drum cut 1/4" deep for a 1/2" drum.I have a drum gauge for both 1/2" and 7/16" drums and in the situation described I would use a small half round file with a medium cut.Most rat tail files are very coarse and mistakes are easy  to make with one.As mentioned,the plate must support the drum with no gap.I have noticed a  lot of antique guns with unsupported drums and even worse placement of the threads in the barrel.I fired an antique rifle when I was 14 and it blew the drum out and my ears rang for 2 days.
I used the gauges I made as a guide and used a milling machine to make the cut.
Bob Roller

[stuckball]

Thanks to all who replied.

[Bob Roller]

One important thing not mentioned.What size is the barrel across the flats? If it's a 13/16x 45caliber there is no safe way to use a drum without making a new breech plug to accommodate the drum.Do you have a tap/drill chart and any experience in threading a hole and an accurate way to drill the hole?There is more to this job than fitting the drum to the lock.
Bob Roller

[kutter]

If you have a drill press or better a mill, the fit can be made to the lockplate and the hole drilled and tapped in the bbl flat all in one set up.

I don't really care for the drum/percussion set up, but the few I have done I clamp the stock with bbl installed in the drillpress/mill vise. Line the chuck/center up with the center on the bbl flat where you want the drum to be.
Make sure you are straight all the way around.

Then replace the stripped lock plate in the gun. Clamp the plate in position,,you likely can't use the lock screw(s) as you can't get at the back side of the rifle now.
Clamping is more secure anyway IMO.

Now the drill or mill chuck is already centered over the lock plate exactly where the drum needs to go.

Use an end mill of the correct dia of the drum to cut thru the lock plate.
Cut down to the surface of the bbl flat and stop.
That will give you a perfect placement & fit for the drum itself in and against the plate.

The keeping everything still clamped solidly in place.,, remove the end mill and replace with the correct tap-drill size for the
threads on the drum.
Now drill the bbl flat for the threads with that tap drill.

Now remove the tap drill and replace it with the correct Tap.

W/O turning the machine on, simply lower the quill down to the bbl flat and using your other hand to hand turn the quill, & carefull tap the bbl threads in. Doing it with the tap held in the chuck assures straight threads into the hole and allaignment with the drum cut-out.

When done, every thing will be in allaignment.
There likely will be a small burr turned up on the bbl flat from the tapping procedure. Simply file that off and only that off.

The drum will fit the cutout you made with the end mill thru the lock plate and be supported by it.

[Bob Roller]

Countersink the tap hole the depth of the 1st thread and avoid the need to clean up the edge of the hole.
Bob Roller

[Bob Gerard]

Ugh. I was thinking about building a nice Pecatonica kit percussion long rifle for the Boy Scout program where we teach Black Powder shooting each summer (Scouting policy doesn’t allow Flintlocks)
I think it might be a bit more complicated than I thought…

[Bob Roller]

No answer to my question as to caliber/bore/barrel thickness or lack of it.If it IS a 45 and 13/16 it needs a plug that the drum can be installed safely in.
Bob Roller

[Bob Gerard]

Bob Roller- would a .50 cal with a 7/8" across flats barrel be safe for a drum and nipple? That would be the size I was thinking about if I was to build one.