Hi Joe,
First off, your inletting looks pretty good, no discernable gaps... Here's my two cents...
The cock is, as you stated, hitting the stock. The wood will most likely need to be removed from that area. There's typically a couple ways you can address that, I like to relieve wood in that area with a round file, creating a "notch" for the cock. Another way would be to create a square "notch" utilizing a flat chisel. Just be careful not to remove too much wood. Blacken the cock with whatever transfer medium you use, then remove wood accordingly... Some locks are more problematic in that area than others.
The lock should be inlet up to the bevel on the lock plate. Once the excess wood for the cock is addressed, the plate will fit down into the mortise. If the lock plate is too deep into the stock, more wood will have to be removed from the panel. If you get a good barrel to bolster fit, and the bevel is proud of the stock, file the bevel to meet the wood of the inlet. Hope that makes sense...
As far as the "slope" meeting the barrel flats... One way you can address that is by removing wood on the "slope" to meet the barrel flats with a flat chisel, or slightly curved gouge. The wood is removed close to the breach area, only going back maybe 1/4" or so. That area is then "blended" back so it's not an abrupt transition. In essence, that area on the top flats is actually concave, but not much. Draw the lock panel as you'd like it be, shape that area accordingly, then address the wood meeting the barrel flats. Again, hope that sort of makes sense...
Many European rifles, and early Kentucky rifles, with big honkin' breaches were able to match the barrel flats without a lot of trouble. As barrels became smaller, the method described above was often used.
This is a photo of a Stevensburg, VA school rifle that hopefully will give you an idea as to what I'm talking about. Just keep in mind that various schools and builders addressed this aspect differently.
