Number one you said you have a lot of confidence in your rig; that is very important. Number two you have a Burris Fullfeild II which is an excellent scope. You have plenty of power with the 9X available. I get the feeling that you also think it is enough scope and I think so too. If you would have access to a chronograph and could get your velocity nailed down you could use bullet drop tables for your bullet to find out how much drop you have at what distances. You could then laminate a small chart to tell you how much hold over to use at which range. You could tape it to your butt stock for quick reference. Range find the distance, look at your chart and then make the hold over and pull the trigger. If you do not have access to a chronograph then make your best estimate at velocity and check bullet drop charts. Then go to a range that you can make long shots on. Check your bullet drop to see if you have guessed correctly , if so the make your chart accordingly, if not then make corrections to your velocity and make your chart. If you want to proof it, either way you go then go back to the range at say 500 yards and do your hold over for that range and see how it does. I hope I did not confuse you here, it really is not that complicated, but some times I make seem that way. I would still sight it in at 3" high at 100 yards.
I am not sure which bullet you are using for sure. If it is a 150 grain CT Ballistic Silver tip for instance the Ballistic Coefficient is .493. Your muzzle velocity would be about 3100 fps + or - a little if you are loading up to full potential. In the back of the Nosler book the tables say with a muzzle velocity of 3100 fps and 300 yard zero you will be + 3.3" at 100 yards +4.0 at 200 yards; -9.4" at 400 yards; -25.2 at 500 yards; and - 48.1 at 600 yards. 600 yards is really stretching it. 400 yards is realistic. For instance if you aimed at the deer's back line you would drop just about right into the vitals. If you were getting 3200fps the the drop would be 8.7" at 400 yards. If it was 3000 fps the the drop at 400 yards would be 10.2" there is 1.5" difference in drop at 400 yards between 3000fps and 3200 fps with a 300 yard zero. Not a whole lot of difference. If you start getting out past 400 yards then it gets more difficult. Then you really have to be more critical with your ranging guessing bullet drop etc. and doping the wind. Not impossible, just more critical. You would hold about a foot or a little more above the deer's back. If there is a 10 MPH cross wind then you will have to hold into the wind about 1 foot too.
I really would not change scopes, you have a very nice one. Even if you changed to a BDC scope you still have to know what the bullet dropis for it to work correctly. I had a BDC scope and it came with different drums for different bullets. Each one had a range that it would work in, so it was guessing too. It also came with a blank one to mark for your exact bullet. I really di not like it that well and used estimating for wind and bullet drop any way. It is an old scope and I am sure they are better now, but I still think you have to do some work up front to range it. Good luck to you. Let us know how it turns out for you.
