Sky, I have used cornmeal as a "buffering" agent in my .69 when shooting shot.
I have always heard that you should mix cornmeal and shot on a 50/50 basis by volume...ie, 1.25 oz of corn meal, should, in theory, equal 1.25oz of shot.
However, with out mixing it on a 1:1 basis in a "paper shot cartridge" it simply is not going to work....even by pouring it down the barrel on top of the shot. the cornmeal is so fine it will settle to the bottom, and lay on top, every time...even with a few good slaps on the barrel, and a couple of thumps with the butt plate on the ground. And, it can not get to the sides of the shot if the shot is poured first.
So, what I've done over time is put the cornmeal in its own little paper cartridge at at a ratio of 1.75oz(by volume) of corn meal, which is opened and dumped over 1.25oz (by volume)of shot, and the paper the corn meal was in is then added on top before the Over-Shot wad is applied....at the same time I have reduced my powder load from 85gr FFg to 70gr FFg.
(Now, why didn't I just roll a paper cartridge with the corn meal and shot inside?.....I have done that, but the transport of such a cartridge allows the cornmeal to do it's trick again, and it is all for naught. )
I started experimenting about 6 or 7 years ago, when Captchee and I discussed shot column height in muzzleloaders on another forum at that time. The important thing to remember here is the longer the shot column (including any additives, CoW, Corn Meal, Grits, or whatever) the more the necessity to adjust the powder charge.....any additives, including any buffering agent, can "blow" the pattern.
The secret, if such can be said, is adjusting the powder charge to the pattern.....too much powder will blow a large hole in the center of the pattern, not enough powder will leave holes on the both the center and fringes of the pattern.
It is a very time consuming process to get a balanced load when using a buffer of any kind....the end result of all this has led me to avoid using fillers / buffers, and shooting just plain shot. However, it can be worked out if one has the patience, and determination.
Just my thoughts......
Uncle Russ...