you have opened, I suspect unwittingly and certainly without malice, a huge can of worms, over which ink in the 55 gallon drum has been spent. (and probably some blood)
some claim that using lead is (to borrow from Faulkner) anathema and apotheosis, and some claim it to be the panacea of all things black powder. the truth, as revealed by Mr. Pletch's most excellent high speed photographs, is probably somewhere in the middle.
you should be aware that some lock makers won't honor the warranty if they determine that you are using lead wraps (I have no idea how they figure this out - but lockmakers are smarter than I by a good bit).
just out of curiosity, I weighed a bunch of 3/4 inch French agate flints, and there was enough variation in the weights so that a smaller/lighter flint with a lead wrap weighed only slightly more than a bigger/heavier flint with a leather wrap, so I don't see how it would ruin the lock, but again, that's just my opinion.
having said all that, I squished some forty caliber round balls in my vise until they were flat and big enough to go around the flint, then I wrapped up the flint and trimmed away the excess. tighten them down better than finger tight, and let the flint strike the frizzen under the pressure of the mainspring (in other words, 'dry fire' the lock, but with the frizzen closed and nothing in the pan). then go ahead and retighten the cock. the action of striking the frizzen will set the stone in the lead, and when you retighten everything, you should be all set. when the flint becomes dull and has to be re- knapped, you'll need to repeat this process.
the theoretical advantage of lead over leather is this: leather (say the proponents of lead) will allow the flint to slightly rebound, which will set up a vibration along the surface of the frizzen and this will result in poor sparks and a washboarded frizzen and the resultant early death of flints. I have seen this in cheap locks with soft frizzens. well make locks, with properly hardened frizzen, and properly set flints do not, in my opinion, suffer any such problems. ( again, just my opinion)
if you opt for leather, I would use thin leather, and wet it before you put the flint into it. tighten the cock as tight as you reasonably can (no cosmonaut stuff) and when the leather dries, retighten it and you should be all set.
in either case, what you want is a wrap which will hold your flint tight and square in the jaws of the cock as it strikes the frizzen, makes the sparks, and fires the pan.
some folks say that you will see a big difference if you try lead vs. leather in a darkened room, but human physiology can be trumped by reality - try staring at something green and then looking at a blank white wall - you'll see the same thing, but not green.
so, there's lead vs. leather
just one guy's opinion: free and no doubt well worth the price.
my best advice: try both and go with what works best for you, and don't get too upset about free advice.
make good smoke!
