I have a nef/ h&r buffalo classic 32in. tube. I just love to shoot this gun its has alot of power for one of the oldest. If I was you I would stick with PMC 300 gr rounds they are about in the middle of the power range for factory loads. But if you want to beef it up alittle try some buffalo bore or garrett bullets. they will rock your world .Just make sure your rifle can handle them. That could be very bad for your rifle or you.The remington 405 gr are the best ones to start with to just get you going. They have the least amout of power from the ones i have shot.
The 200 yard shot you are talking about would be hard to do unless you practice alot. I can shoot that far pretty good but it has come from lots of bench time. This is a very good round for deer and you will find between 0-150 yards its hard to beat.