I have two items that I'd like to make cartridge powder measures for. The first is a golf ball sized stainless mortar that really does not have a powder chamber, just a depression in the bore where fuse and bore meet. The manufacturer gave me a laundry scoop for the suggested "blank load". The next is a vertical three shot signal device again with no powder chambers, just bore which is 1 3/16" diameter by 3" long. Now I've heard a cheap and easy formula for blank charges in any size cannon is to take a cylinder of bore diameter and have it as long as the bore diameter. So in this case it would be a cylinder of 1 3/16" diameter by 1 3/16" long. In this short signal cannon that would end up being about one third of the barrel's bore (ie. one inch of powder in a 3" long bored barrel). The maker was giving me suggestions in number of tablespoons (heaping at that) and there is no consistency in using a heaping tablespoon to measure powder. After I figure out my load for the three shot number I thought of my case for measures for both. I'll take two 50 BMG cases that I've drilled and tapped the primer hole to say 1/4 X 20 and loctite the threaded end of a brass machine screw where it's not protruding into the case. After the loctite hardens I'll cut off the remaining portion of the screw and polish it flush with the bottom of the case. Then I'll measure the extractor groove and drill that diameter hole in each end of a flat piece of 7" long by 1/8" thick piece of brass. At the half way point of each hole I'd Dremel the end half of the brass off. That way the half a hole would slide into the extractor groove for me to solder together. It would sit flat and be able to service my three shot signal cannon and my golf ball sized mortar. Since I've made a mortar bed with steel reinforced brackets for both signal devices, I would then be able to chain the fusing together so that the three shots would individually go off in sequence to be followed by the big bang of the golf ball mortar. Great fun on the fourth I'd bet. Do you folks think that a cut 50 BMG case would hold the powder that I need for each of these? By the way, the laundry scoop is a small one, not a cup in size but more like the ones found in concentrated laundry soap. Smithy.
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