In my experience :idunno: with a drill press and just a handful of tools you can make your own 'chambered' breech. But then again, I work by the T.L.A.R. Method ( That Looks About Right :thumbsup: )
On mine I set the barrel up on the gun. Making sure the barrel and breech were index marked, so I could return them to the same position..I Located and then drilled the position for the nipple using a smaller "pilot" bit. measuring and drilling so the bit came in to just about center of the BP diameter..
took the barrel off and un-breached the gun. using dykem ( or a black dry erase marker ) and I colored the face of the plug.
Using my centering tool and a scribe.. I marked two crossing lines on the face of the plug ( or bolt in my case) with the plug held in a vise I used my center punch to put a locating 'pip' at this intersection..
with the drill press OFF and UN-Plugged :wink: I used a smaller bit, for a pilot hole and chucked it up.. I Set the breech plug up in my DP vise and using the square, against the bit and the BP I got everything as square as I could to each other.
then I moved the vise so the BP was under the bit and made sure the pilot drill would seat into the the lil Pip I had made on the face ( see above)
once I everything was set.. vise locked into position,plug held tight and square to the bit/quill.. I plugged the drill back in and started it up.. now using just a light feed and some cutting oil I let the bit pick up the pip and get itself started.. then it was just a matter of drilling to the depth of the intersecting hole ( you had previously drilled for the nipple )
once I had reached the depth I wanted?? I swapped to a larger bit and drilled the plug again.. to create the final chamber size.. then I took a countersink reamer.. and with a piece of manilla folder between it and the plug,, I cut a slight chamfer to the face of the plug.. making sure it still had enough diameter to seat/seal against the breech..
after that, it was clean everything out.. re-install the plug in the barrel and finish drilling and tapping for the plug!! Voila' a chambered breech.. or my attempt at them :grin:
Kinda long winded.. easier to do than write about.
I'm certainly no expert < and some opinions may differ on the work?> but that is how I have done mine..
Respect Always
Metalshaper/Jonathan
one caveat..make sure you breech chamber is shallow enough,, that when using a reduced charge, you're not creating a mini "short start" situation!!!