Hey Drail,
If I missed something here, please forgive me, but I did not find anything that indicated whether you reloaded shotshells or not. It also seemed to me that you are mainly interested in buckshot loads.
If you do not reload shotshells, and you have problems with buffer leaking out of factory loads, I would think the manufacturer should be making buckshot that is sealed perfectly. I haven't bought any for nearly 40 years, but the last ones I bought (Remington 20 guage) are still factory sealed with the crimp petals melted together. They are still in like new condition, and I would not hesitate to use them. I never had any need to seal them.
If you are able to load your own shells, I can give you an idea of how I build mine. For 12 guage 2 3/4 shells, I use Remington STS hulls with 16 #1 buck balls. The #1 buck shot are not quite as big as 00 buck, but there is not that much difference. I use 34 grains of Blue Dot under an old Alcan wad stuffed with 100 pounds of wad pressure. The old Alcan wad has a plastic base to seal the powder, and a fiber pad on top that is about 1/4 inch thick - it has no petals. I then stack the 16 #1 buck two per layer, with each layer turned 90 degrees from the layer below. I find this loading brings the 16 buck shot right up to the top for an excellent crimp. I then put 17 grains of plastic buffering material in the hull. When adding the 17 grains of buffering, I let the hull vibrate a bit against an electric powder trickler as I pour the buffering in. When the shell is built in this manner, all 17 grains will flow in and around all the voids in the buck shot, and it will come all the way to the top of the balls. I then do the half crimp stage and then the final crimp stage. At this point, at least 95% of my buck shot shells are perfectly formed, and I then seal them with candle wax. I drip enough wax to cover the crimp a little over 1/16 inch thick (perhaps 10 to 12 drops, and I do this for perhaps a half dozen shells at a time. Then I take those six shells and run them up the final crimp stage a second time to form the soft wax tightly into the crimp folds. The wax does not stick to the crimp die, and it is a rare wax seal that cracks later - even after sitting for years at a time.
I have tested these loads at 25 yards with my Winchester shotgun rated at a full choke, and the spread in that gun is about 18 inches. When I tested the same load in my Mossberg 20 inch cylinder bore shotgun, the spread was closer to 28 inches.
That may not be what you wanted to know. If so, I again beg your pardon. If it is useful, it is my pleasure.
Best wishes,
Dave Wile