I think it depends on your specific needs. Bolt gun is going to be lighter to carry around, and likely tends to be a little more accurate. AR gives a faster follow up shot, but is heavier to carry around. With 1-6 magnification, I don't think accuracy will be a relevant topic of discussion, so just depends on how much weight you want to carry around vs how fast you want to be able to take a follow up shot. Personally, based on the trajectory, I think the 450 BM is more of a 200 yds deer cartridge.
I don't own, and haven't used a 450 BM, but based on the information above, I'd say that the terminal performance is EXTREMELY similar to my Savage 10ML-II muzzleloader which I used exclusively during firearms and ML season in Indiana for over 15 years and normally took 2 or 3 deer with it every year. I started off shooting 250gr SSTs over 2600 fps. I don't recall the load data off the top of my head. I took deer anywhere from under 10 yds to just over 200. I never had an exit wound while aiming at the boiler room. What was left of the bullet was ALWAYS laying under the hide on the far side. Meat damage was excessive, but I was younger then and didn't care because the deer were plentiful. I normally lost at least 1 front shoulder and most of the meat on one side of the rib cage. I don't have an accurate way to describe what the inside of the chest cavity looked like. The closest I cold come is that it looks like a prairie dog was hit by something running 4000 fps, but the PD had Kevlar skin that didn't allow it to be blown apart. Around 2009 I switched to a 300 gr SST over a stout charge of RL7 for 2450 fps. After that, I always got an exit wound, and the meat damage was still excessive. You could usually drop a baseball in the entry wound. It would take a large part of 3 or 3 ribs with it on the way in. Exit wounds were always bigger than a golf ball, and always took out at least 1 rib. I did a lot of ballistic testing and found that at those speeds, most 250gr cup and core bullets did not produce a straight wound channel. The were prone to veering off course, presumably because they had completely flattened out. Many times I would have to repeat tests because the projectile would exit the side of the ballistic gel. The exception to this were the Barnes 245gr monolithic projectiles. They did not over expand, and they always produced a straight wound path. Conversely, all of the 300 gr projectiles I tested also produce a straight wound channel. Prior to buying my Savage in 2003, I had used an Encore with some pure lead (ie soft) conical, and they did some weird things on impact, often taking a hard turn to the right or left when striking a rib or shoulder. After seeing something similar with my Savage and the 250gr bullets, I switched to 300 gr and never looked back.
A few years after Indiana legalized rifles for deer hunting, I bought a 6.5 Grendel upper. I still use the Savage during ML season, but the Grendel kills them VERY dead and I don't loose nearly as much meat. If I had to use a straight walled cartridge, I'd probably use a 350 Legend instead because I think the terminal performance would be more appropriate for deer size game.
These were my results with a slightly different cartridge, so your mileage may vary.
