I dont know about buckshot, I never messed with any shot that large...but, I have a shot machine and with the smaller bird shot like I make the way to get it to look like factory stuff is to put it in a vibratory tumbler, like for cleaning brass cases, and add some graphite and turn it on. It will give it that dark color and also give it that shine. I don't know if it flies any better, as I understand it the factory does this to help it meter through the loading machine/reloader.
I do not tumble my home made shot in graphite, I just load it and go shooting...it seems to meter and fly just fine, or at least I cant shoot good enough to tell either way. I think lee makes buckshot molds that have a little thin lead "string" made into the mold...keeps all the buckshot together for a tighter pattern. Haven't tried this mold, but if I had the need to shoot buckshot I think that is how I would go!!! At least it sounds good anyways.