I've refinished a Manhattan 22, and in polishing down the frame I found three plugs pf copper, one round, 2 rectangular. Knowing that copper melts at a much lower temp that steel, it is safe to presume these were added after the casting. These plugs were not to fill modifications in the original design. Was this type of repair on casting flaws typical practice on small caliber guns that were to be plated? In the pic below, the brass is an access port to install/repair the internals.
Nice job on a gun that probably never had it so good when it was first made. I think you might be right in thinking that it was a matter of setting up the gun for a smooth nickle finish. Since these guns were hardly practiced with, if at all, the matter of the heating point would never really matter. Also, the cartridge involved was akin to the .22 CB cap of today (only with less power).
Don't know the answer to your question, but wanted to 1) compliment your work on a nice gun and 2) let you know that there's a decent book out there on these Manhattan firearms (easy to find for under $20 these days).
