tOBias: Welcome to the Forum!
I am looking at a picture of a CVA Hawken and it looks just like the CVA Hawken I had years ago.
By that I mean, it has a side "drum" which the nipple screws into. This is a round bar about 1/2 inch in diameter sticking out the side of the barrel.
It may have a "clean out screw" going into it from the outside. If it does, remove the screw and the nipple and use a pipe cleaner wetted with water to clean out the channel which connects the nipple with the bore of the barrel.
That should solve your missfire problem.
Oh, also when you load your gun, make sure there is no cap on the nipple, and that the hammer is at "half cock". The idea here is to leave a vent for the air inside the bore to escape thru, and in the process it will blow some powder back under the bottom of the nipple. This should provide instant ignition every time.
If your using real black powder, you should not need hotter precussion caps. If your using Pyrodex or 777, the hotter caps will provide better ignition.
If you can't find RWS caps, you might look for CCI Magnum caps. They work just as well, they cost less and more places have them.
The guy who said you need a new breech plug is full of...let us say, bad information. (we can't swear here because the owners daughters read these things).
The breech plug on a side lock gun is almost Never removed. In fact, on some guns like the Thompson Center Hawken it is almost impossible to remove.
On a gun with a precussion side drum, the breech plug has absolutely nothing to do with ignition.
As for the Sabots and the 100 grain loads, I suspect the guy is giggleing every time he thinks of telling you that.
There is absolutly NO reason for you to punish yourself with that kind of load. Not even for hunting Deer.
I would suggest that you buy a box of .490 or .495 diameter lead balls, and some .015 patches. If you can't find patches, buy some tightly woven COTTON cloth which is about .015-.018 thick. If you have access to a WalMart, buy some blue and white striped, or red and white striped "pillow ticking" for the patching.
Lube the patch with the commercial "bore butter" stuff or Crisco, or Vegetable oil, or just spit.
For a .50 caliber gun shooting round balls, start at about 50-60 grains of powder (FFg, FFFg, Pyrodex P, Pyrodex RS or 777). Black powder is best.
When shooting this load you will be amazed at how much fun you can have without being kicked to death.
With a 70 grain load, you will be shooting a 180 (roughly) grain bullet at about 1550 FPS. Far from puny, it still won't kick hard. With a 90 grain load and a round ball, your gun will, with a well placed shot bring down an elk with one shot.
Another good thing about shooting the patched balls. MONEY.
The balls will cost you about 8.5 cents each and the patch will cost from almost nothing (if you make your own) to about 5 cents each. Most of the Sabots I've seen cost more than that without the bullet. Give it a try.