Gentlemen,
Thank you all for your input and tips, I really appreciate it.
When I came back to reenacting the RevWar in the late 90's, people seemed to be having more problems with their locks than we had when I reenacted in the 70's. Part of the problem in the 90's forward was there were far less reenactors who were also shooters, but a huge part was the muskets or locks themselves. I never had problems with powder staying in the pan with my circa 1970's Italian Brown Bess, but that was a huge problem in the 90's forward.
In 18th century musket drill manual for loading, one primes and shuts the pan while the musket is up in your hands in a position somewhat similar to the modern day "port arms." Then one "casts about" the musket and that means you turn the musket and lower it to the ground to load the barrel. That movement is supposed to be done sharply and quickly. (If soldiers were not well drilled in doing the loading manual precisely and sharply, they would be very slow in loading and that meant their life was in more danger.) When doing this technique sharply, many reenactors lost most or even all of their priming powder as it got "slung out" of the pan. The problem came mainly from extremely poor fitting of the frizzen to the pan on so many repro muskets. The Japanese made Brown Besses were worse for that, but even some fairly recent Pedersoli muskets had the problem to a lesser degree. I wasn't trying to waterproof the locks, especially, just keep the powder in the pan while the musket was sharply moved about.
I probably should have mentioned that I included fitting the locks to the barrel and relieving the corners so they don't dig into the softer barrel steel. Some of the locks fit the barrels so poorly it wouldn't have mattered how tight the fit was between pan and frizzen as they lost powder between the barrel and lock. However, that wasn't as much of a problem as the large gaps between many pans and frizzens.
When I'm talking about distortion after heat treating, I'm talking only a few thousandths of an inch or less. Just enough that it opens up what was almost a fit where you couldn't see hardly any light anywhere around the pan to the point in some spots you could see light or a little more light afterwards. From my background of hand fitting NM .45 pistols, a single thousandth of an inch is a large tolerance when fitting slides to frames or slide stop pins to match barrels.
It seems I was "over working" the fit of the pans to frizzens locks a bit and that's what I needed to know.
Thanks again, Gus