200yds is My Max with a Mler, it does'nt have the Velocity as a Rifle at Long Distances, too much can go wrong at 150+yds let alone 300. I have actually watched as My Sabot struck the Deer I was aiming at, at 80 yds, you would'nt see that with a Rifle Bullet.
If you want a Scope with a DBC try the Leupold Ultimate Slam MLer Scope, it has settings for a 2 Pellet (100) Grains of Powder with a 250gr Bullet, a setting for a Shot Gun, and a setting for a Mag Load of 3 Pellets, 150grs with a 250gr Sabot. You just zero in with your set up and the Scope will do the rest. Now I know most dont shoot either 100grs of Pyro with a 250gr Sabot or a 150grs of Pyro with a 250gr Sabot or will use this scope on a shotgun. Reguardless of what you use, and even if you use any of these Loads for your Mler, you'll still need to check the marks to your hits on the Target with the BDC. The Leupold Ultimate Slam has settings for yardages out to 300yds.
Now here's what I found out about the BDC, You Dont Need It. Who has time to break out a Rangfinder to see how far the Deer is so you know what line on the BDC to hold on, it's nice for Target Practice so you'll now exactly where to hold but for real life Hunting Situations when you only have seconds to make the shot it's not what I prefer, even though I do have this scope on My MLer, I quit using the BDC.
I sight in My MLer at 2" at 50 yds, if I hold on a Deers Heart at 20 to 50 yds Im on, anything further out to say 175yds I just hold dead center lungs and Im good.
I can actually hold dead center lungs from 0-175yds and be in the kill with no problem with 2" at 50yds, but the Close shots will be a tad high in the lungs but still do the job. If you can remember to hold in the Heart Area at Close shots and to hold in the center of the lungs as longer distances, the 2" high at 50yd sight in works great for most MLer Loads and Shots. This way I only have to remember to just hpld dead center lungs for all my shots and Im in there.
(BP)