The project started with this old damascus percussion barrel and a beautiful left-hand percussion lock that D. Taylor Sapergia kindly sold me.
https://americanlongrifles.org/forum/index.php?topic=57924.msg579837#msg579837 This is how I solved it, comments and suggestions for easier solutions are wellcome.
With the plug out, the next step was to make a lefthanded plug. This picture shows the tools used for carving the snail.
20mm ball punch (top left)
Set of cheap diamond burrs (middle left, two sets, coarse + middle fine, eBay, 13$ a set)
Barret needle file #2, (bottom left)
Two rotary files
12,5 mm short drill
14mm ball nose endmill.
I started with a piece of 45mm mild steel round stock.
The threads on the original breech plug proved to be M17. I turned down the threaded portion to 17mm and threaded it in the lath using a M17 Die. Getting a M17 die proved to be a challenge. It is an obsolete thread, and no one stocks them in Norway. Die size jumps from M16 to M18. One supplier in Norway could get me one from Germany for a little over 100$. Quick search on eBay, and I got one from China for 12$ including postage. It did the job perfectly, but I had to wait 8weeks for it.
Next, I used a 14mm ball nose endmill in the lath to drill the powder chamber. Sorry forgot to take pictures. I then fitted the threaded portion using Prussian blue, so it fits tight to the bore shoulder and the end of the breech. It turns out that the original plug was a sloppy fit, with a gap about 1/32” between the plug and the bore shoulder. Since the new plug is threaded with a die, I had to remove the last one and half threads to get it tight up against the barrel. The plug has five and a half threads. Should be strong enough.
I could have gotten away with using a smaller diameter of round stock if I turned the threaded portion off center. I chose not to because, this way I did not have to worry about timing the plug. Just cut the snail wherever it fits.
Mill down the top, bottom, and right side of the plug. The snail going to be on the left side. Leave the sides 1/32” oversized. This will be fixed when drawn filing the barrel and plug together.
On the left side, mill the snail blank to match the bottom corner of the left barrel flat.
Remove as much waste material as possible from the diagonal flats by milling stepwise.
The top of the snail can be broken down to a series of circles drilled off center and blended in. Mount the blank in the mill at the needed angel and drill out with the 12,5mm drill. The hole defines the outer perimeter of the snail.
Next is the flat bottom of the top face. It is done with a 10mm end mill. The center is inline with the top corner of the left-hand barrel flat and a little towards the rear of the plug.
The base of the nipple is 7.76mm. Mill out the nipple seat with an 8mm endmill. Start the hole for the nipple with a center drill.
Drill and thread the hole for the nipple (1/4x28). The depth of the hole is a hair past the middle of the left barrel flat. Use a bottom tap.
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Start scooping out the top face with a 14mm ball nose end mill. Locate mill so it touches the left side of the 12,5mm hole and as close as possible to the front of the same hole.
Start filing out the front of the snail, following the edge of the 12,5mm hole. Slope and blend in the right and left side of the top face using rotary files and diamond burrs. The burrs fit in a Dremel. The rotary files are too big for the Dremel and I used a regular cordless drill. This shaping left a lumpy surface an uneven curvature. This was smoothed out by cold forming with the 20 mm ball punch. The surface was finish off with valve grinding compound and polishing pads for the Dremel. Sorry, I forgot to take pictures of the whole process.
File out the side profile of the plug and mark off ample extra room for the shield. I use about 1/8 “. If was going to start over again I’d use 3/16”. The shield is dough out with coarse diamond burrs.
It is hard to follow the curve when starting the groove with small pointed burrs. I needed the extra material to smooth out the groove using cylinder shaped burrs. This process moves the groove closer to the edge off the shield. To get the groove deep enough, you must dig in with pointed burrs which moves the curve further to the edge. Also, when focusing on the tip the burr following the groove, its easy to forget the where the rear of the burr is pointing and get notches in the shield. I ended up with a shield that is a bit smaller and thinner than I wanted. I had to throw away my first attempt, so this one will have to do. I lack “the get up go” for a third attempt.
Digging out the shield with burrs leaves a slightly rounded bottom of the groove and blurs the definition between the snail and the shield. I used the tip of a Barrett needle file to get a sharp corner. The barrett file was also good for smoothing out the inside of the shield.
The shield was then polished with valve grinding compound on a stick (took quite a few hours).
I drilled a 3,3 mm hole from the right side of the plug which intersects with bottom of the nipple hole. A 3,0mm hole was then drilled in the lath from the center of the powder chamber to connect with this hole. The bottom of the nipple hole is cleaned out with a ball diamond burr.
The right side of the hole was threaded for a M4 bolt, made from the same stock as the plug and peened shut. The hole in the powder chamber was the re-drilled to get rid of the protruding bolt.
Next, I milled out the hook of the breech plug.
The last step was to draw file everything so the profiles of the plug and barrel match.
Finished breech plug compared with the original.The shield should have been a bit larger, otherwise I am happy with the result. Took me about 25-30 hours to make a plug.
Barrel with the lock from Taylor.I am planning to make a Le Paige style pistol and inlet gold wedding bands on the barrel.
Next step is to make the standing breech tang and find a nice walnut stock blank.
Best regards
Rolf
PS.I have some questions regarding the standing breech and will post them in a separate thread, so they do not get lost in this thread.
