200yds with ONLY magnum capable BP rifles (150 grain loads in quality in-lines) is a VERY VERY capable proposition for most folks. I think alot of guys are under-estimating their own abilities as well as that of their guns. With something like a Encore/Omega/Knight Disc etc firing 150grn loads with 250grain bullets like SSTs or Barnes, the typical drop @ 200yds is 6" when sighted dead on @ 100yds. They drop like anvils once you cross the 225 range (but still are killable at 300 with practice) and I personally recommend something like a mil-dot setup. All of the above loads and guns will still produce around 1k ft pds of energy at 300yds so at 200yds they are more than adequate for deer sized game.

When dealing with loads under 130 grains of propellant I would recommend 150yds as the maximum for most shooters,
RA