The original post was kind of long and picking flints is a bit long also...I figured if anyone wanted to know they would ask.
Picking Flints:
1. They should be of correct length and width. The leading edge should be the same width as the frizzen face. The length should be such that it doen not touch the frizzen face when the piece is at halfcock.
2. They should have no inclusions on the leading edge...best if they have no inclusions. An inclusion is a discolored line and is guarenteed to break at that point. I have several flints with inclusions on the top, bottom, and back of the flint. This will have no detrimental effects.
3. The top of the flint should be flat. Many flints have a top that looks like the peak of a roof. This is not desirable as the jaws of the hammer will not hold the rock securely.
4. The flint should be of sufficient thickness as to be held securely in the hammer jaws and increase durability. If it is too thin, the jaws may not tighten enough to hold the rock.
5. The leading edge must taper nicely to the flat top. The back edge should have some taper. If the taper is too long, the leading edge will be too brittle and not hold an edge. If too short, it will never take a cutting edge. Some flints taper on both edges. Sometimes they work pretty well, as you can use both edges when shooting.
6. When striking the frizzen, the leading edge shatters a bit. After a number of shots, you will have to dress the leading edge to maintain a good spark. The best way I have found is to cut the tip off a nail and put a 1/32" shoulder on it, 1/4" from the now blunt tip. Put the shoulder on the leading edge and tap the head of the nail with the handle of your knife. This should flake off a small portion of the leading edge, sharpening it. Please do not use a knapping hammer. This will destroy your rock in short order.
7. Determine which way the rock is placed to get a good spark. Most guns like the flat top up, others like it down. I found that flat up works best until the rock startes wearing down. Then I can shoot it one way and just flip it over and keep shooting. Remember, the leading edge shatters on each shot. By flipping it over every once and a while, it is almost self sharpening. I had a flint with a long back edge once and got over 150 shots from one flint!
8. Place a piece of leather in the jaws to hold your rock. The jaw screw should pass through the back of the leather, holding it in place. Cut to fit while in place. Grease with bear oil, or your favorite patch grease. The purpose if to keep it water resistant. Lead was used for military guns, but is very destructive to the rock and hammer. It takes a hell of a lot of pressure to hold it in place with lead. The leather absorbs some shock and protects it better than lead.
9. Store your flints in a clean, dry environment. Rock does absorb water (ie: river rocks). I wrap mine in a piece of leather and wrap tightly, so the leading edges do not shift and wear each other down.
10. Always give some away. Someone will need one and won't know crap about buying flints. Give one to them and show them what to look for in a rock.
NOW you know why I didn't post this with the original :-D
I have to go soak my typing fingers and figure out how to post pics. If anyone has questions, please feel free to drop a line.