The Loopies for 450 Bushmaster will be close too. Ballistically speaking, a upper end 250gr SST ML BH209 load is pretty close to a 250gr 450BM load. To me though all this BDC talk and especially 300 yard stuff is a moot point. Common loads will be garbage by the time they reach 300 yards. FPS/FPE will have fallen to pathetic levels and them ML BDCs are usually for something like a 250gr SST@2100fps+.
Just get a good scope and figure out the max point blank range for your zero. Something like zeroed at 150 will be close to point and shoot to 200yards with a good bullet like a Parker BE or Fury. Then practice shooting to 200 yards. That Diamondback HP will handle that with ease and cost you $100 less than a 3x9 Loopie Ultimate Slam. Plus the Ultimate Slam reticle is kinda trash. I had one in a Redfield when Leupold was making them.
The 450BM Leupold has a duplex reticle with a turret calibrated for a 250gr FTX at 2200fps. A 120gr load of BH209 and a 250gr SST is almost that fast.
The VX-Freedom® 3-9x40 .450 Bushmaster® is ready to rock right of the box. The 3-9 model provides the ideal magnification for most shots, while the custom engraved dial is already calibrated for the unique .450 Bushmaster round.
www.leupold.com