"Yep. All you need is an approved form 1."
Oh, and some machines and tools. And skill. The 1887 would not be an easy gun to make, at least not the way it was made back when.
And remember, if you get Form 1 approval to make a gun, YOU have to make at least the frame. You can't get anyone to make it for you, or take part in the actual making unless he has a manufacturer's license. YOU have to make the frame, then you can buy the other parts or have them made.