Arcticap, Actually I was misstaken. The CVA and Lyman BP design are very similar. Last night I spent several hours reading post about BPs and modifying them. This morning I read your post and then revewed several from last night. Even though Doug at Western Powder said their Blackhorn 209 powder was not compatible with the Lyman Mustang ML. I was determined to try some more to get it shooting.
Doug had said the BP design was to large, holding the Primer loose and had too much head spacing. Allowing the prime to slide back when fired. I couldn't do anything about the BP size, but the head spacing??
This morning I pulled the BP from my CVA Kodiak Magnum and compared the two. The Lyman flash channel was much smaller than the CVA. I could easily slip a 7/64 drill bit into the CVA flash channel, but not in the Lyman. So I drilled out the Lyman BP flash channel with the 7/64 drill bit. I left the vent hole as is.
To correct for the head spacing,: The lyman BP has a small flange just before the the 1/2 nut, which butts against the barrel when tighten. Took a small piece of thin electrical solder, cut it just long enough to wrap it around the BP with out overlapping the ends. I screwed the BP in and tigthen it. When I got near the end I went slowly, I put a primer in and placed a small drill bit on top of the primer. I tighten the BP so that the drill bit rested on the breech face and I could just barely see light between the primer and drill bit. I tried closing the action several times, no problem with the primer. This eliminated the extra head spacing and held the primer in plcae when fired. I pulled the BP and measured the solder. It had been compressed to a tickness of .0026. I repaced the BP with a ring of solder.
I then took it out in my yard where I have a rifle range. First I fired several CCI 209M primers. They sounded louder. So I loaded the gun with 50 grains of Blackhorn 209 powder (weighed on a powder scale), a saboted bullet and another primer. I aimmed and fired the gun. The gun fire hitting the 2" orange dot.
I moved back to 100 yards. Second shot was a hang fire. Shots 3 through 10 all fired fine. Eleven was another hang fire. I held the gun up towards the sun and tried looking through the flash channel and vent hole, it was plugged. So I cleaned the flash channel with the 7/64 drill bit an blew from the end of the barrel clearing the vent hole and flash channel. I fired nine more shots, all normal with no hang fires.
During the firing session, I would weigh three powder charges in my gun room, go out and fire them. Then go in and weigh three more. While in the house a Lyman customer service rep returned my call. He proceded to tell me that the Blackhorn 209 powder was not compaible with their ML, that they had done numerous tests and it just would work. After seferal minutes, I interrupted hime and said I had just fired a dozen shots with BH 209 powder. I paused for several seconds and then asked what did I do to get it to fire.
I told him the Primer pocket had to be about .002" smaller, the primer nipple had to be about .0023 to .0025" longer. Flash channel about .1130". All easly done in their machining process.
That ended my firing for the day, but the two hang fires were in the back of my mind. I wanted to go larger to ensure I had good ignition in cold weather. So I looked up the next size larger drill bit. My 7/64 drill bit measured at 0.109375", a #34 drill is something like 0.1103"; a #33 drill bit is 0.1130". This afternoon I purchased a # 33 drill bit and again drill out the flash channel in the Lyman BP. I haven't shot it yet, but the # 33 drill bit fit into my CVA BP.
This had been the first time I used Blackhorn 209 powder. My thoughts: It was cleaner. I fired ten shots before swabing the barrel, never could have done that with Hodgdon Proydex pellets. It seemed more accurate with the little firing that I did.