I remember your first post
Bluegunner and, as a Mustang owner, have been looking forward to your report.
For a long time I refused to pay the price for Blackhorn because I do a lot of shooting (about 20 lbs. of T7/GOEX/Pyrodex in the last year). Well, last month I broke down and bought one canister of BH. I was not too hopeful because I've converted the two breech plugs I have for the Mustang to .25 ACP ignition and suspected it might not ignite BH.
Well, I gave it a try under my favorite hunting bullet - the .452 300 grain Speer Gold Dot in a Harvester short black sabot. This is the best shootin bullet in my Mustang with 105 grains of T7 or 120 grains of GOEX. With either powder I can pretty much expect five-shot 100 yard groups to be in the 1 1/2 to 1 3/4 inch range.
With the Blackhorn I had a number of failures to fire, but got it to go off with CCI small pistol magnum primers. However, I had hangfires - from slight to major - with every shot. Considering the hangfires it shot OK. I did wipe the bore with an alcohol patch between each shot and that may have been a mistake. Anyway, I've got a new 209 breech plug arriving in another week or so, and will repeat the test, and try it without wiping the bore.
Here are the targets from my first shoot.