Taco,
You are right about function over form being important, and that is a good lesson. As a new builder, I have been obsessed with form and improving my skills.
I am of two minds about the finish on the barrel and lock. I try to stay accurate to what may have been done at the time.
I will likely leave the lock in the white.
For the barrel, I may fire blue it or charcoal blue it. I think fire blueing is probably more correct historically. I do not intend to brown it.
Cheers,
Norm