A blacktail isn't the same as a big whitetail, and it doesn't follow that what works on one will work equally well on the other. A .243 or a .30/30 is far ahead of buckshot, and I'm not all worked up about the .243 for game much over 100 pounds. A 00 pellet weighs 50 grs, and due to it's light weight for caliber, each pellet looses velocity rapidly after impact. If the pattern has opened up, the wound is less effective than if the pattern is tight at impact, but this means shooting within 30', and 10 yards isn't very far. Once the range has exceeded 25 yards, you might not even keep all the pellets on target, further reducing the effectivness of the charge.
Compare the individual 50 gr 00 pellet to a .243 bullet that weighs between 85 and 100 grs and impacts at nearly 3000 fps. If the bullet performs as designed, the center of gravity moves forward as the bullet expands to .40 caliber, and soft tissue is crushed by the supersonic shock-wave that comes off the expanded nose at roughly a 45 degree angle. Due to the bullet's rotation around a linear axis, and its weight forward attitude after expansion, penetration is straight and the bullet is unlikely to be deflected by a bone provided it stays intact, although the high impact velocity provides a challenge for a traditional jacketed bullet. If the bullet grenades inside the chest, the damage will be quite impressive, though shallow. IMHO, a .30/30 performs better on deer sized game with less velocity and more bullet mass.
