Not familiar with the Bushnell BDC, but the Leupold Mark AR fire dot SPR reticle I have is right on with the load it is calibrated to, the 62 gr. M855 load. It has hold over tics to 800, I have shot it out to 500 and the elevation was right on. But I had to do some windage correction at that range. Any BDC should be shot at various ranges with the ammo you will be carrying in your rifle. Your line for example, 400 yards, might actually be on for only 350, depending on the load you are shooting, how high your scope is above the bore, your elevation above sea level, etc. Also, I have sighted in for 100, then find out at 400 or 500, that my bullets are hitting 9 inches to the right, almost missing the target. You need to sight in for the longer ranges, and not worry so much about where you are hitting at 100, it will still be close enough to hit, unless you are picking off flies at that distance. So get a big piece of cardboard for a target, and find out why you aren't hitting the target when holding at the 300 yard mark, and adjust accordingly. I would rather be hitting an inch ( or even two) to the side at 100, than missing the target completely at 300. Sight in so you are, say for example, hitting dead center at 300 with your 300 BDC mark, and don't worry if it's off a tad at 100.