I pour and load my own buck shot. I do it with 12 ga but not 20, yet... I purchased the DO IT brand sling shot mold and it makes #1-0 buckshot and 00 buckshot. It will pour 11 small pellets and 9 of the big ones. I uncrimp a normal skeet shell and melt the lead in with mine. then repour and let cool. In a 12 ga the small #1 stacks very nicely into the shell. I get 3 to a level and 9 in a 2 3/4 shell. the pellets ride inside the shot cup and this does 2 things. It keeps the buckshot from spinning as it travels down keeping a better down range pattern. It also helps keep the shot from deforming. Lead tire wheel weights make great shot because the have a small ammount of tin in them, making it harder and less prone to deform. I have not used buffering in my shells because they stack so well and i have killed coyotes To to 70+ yards with mine. My next batch will have buffering tho. For a 20 gauge I would think that you may only get 6 pellets in the shell. I will likely mix and match sizes to make it fit. I would think Buffering would be MANDATORY for any shell that does not stack well. many things have been used for buffering, however ground corn cob would likely be the easiest/cheepest thing to use. It is found for conditioning reload brass, and pet bedding. From what i have red IF you combine buffering with keeping the shot cup you will keep pretty good groups... BTW you need to tamp the small ammount of buffering with each level of shot... Good luck!