Buckshot is normally used for deer hunting at very close range or home defense.Buckshot comes in several sizes #4 being the smallest and 000 the largest. You should be able to find the actualpellet sizeonan ammunition makers website. You may want to try the Remington site, it normally have alot of good info.

If my old memoryis right, 00 Buck is 32 cal and 000 is 36 cal but I could bewrong.