mechanic & TRM-1,
What rifle/breech plug are you shooting it out of? What primers are you using? You need a breech plug with a sealed primer pocket, they have a picture with the type that works and don't work. You also want to use the hottest 209 primers, Federal 209A and CCI 209M are the best IMO. The biggest problem while shooting Blackhorn is keeping the flame channel clear down to the flash hole. If I had to bet, I would bet your flame channel is full of carbon from previous range sessions. It is very hard to detect, because there is ususally still a small hole all the way down to the flash hole, and this give people the false sense of security that everything is clear when it is not.
For the T/C and Knights a 1/8" drill bit is perfect for cleaning out this area, just turn it in by HAND and you won't believe how much carbon can build up in there. You may want to start with smaller diameter bits and work your way up. This carbon build-up not only prevents alot of your flame from reaching the flash hole, it also robs much of the heat and pressure, since the gasses are pushed back around and through the primer.
On the CVA and probably Traditions too, you have a metric hole, but I think I have read where a 7/64" drill will work on those.
If your saboted bullet is a loose fit, it only compounds the problem when your flame channel is full of carbon. Blackhorn 209 needs the bullet to be seated firmly on the charge, and needs to remain that way long enough for the heat and pressure of the flame to ignite it.
The first time you remove this carbon, you will swear you are removing metal, it is that hard, but once clean you will see the difference. Here is the set I keep in my range box, they allow me to even clean out the Knight bolt actions plugs with the quick connect handle. DO NOT chuck up these drill bits in an electric drill, just turn them by hand and you will know when you reach the bottom of the flame channel where the flash hole starts. For best results you can do this every group, every other group, or you can go a dozen shots or so. If you have never done this, I would bet my best rifle that this is your problem.
I did some extensive experimenting starting back in April 2008 with several different rifles/breech plugs/ignition sources, Blackhorn 209 NEEDS three things to go bang, Heat/Pressure/Time. If one of these is not up to par, you will not like the results.