Does your false bottom sit right at the curve for the bottom of the keggle? I have a Coors keg keggle, which might be slightly different than a BM keg, but about .5-.75 gallons of liquid fits under the false bottom, so you figure the volume of the keg - the false bottom is somewhere between 14.75 - 15 gallons. How much grain you could fit from there would depend on how much water you intend on using. You could fit a good bit of grain (30-32 lbs or so) if you were doing a high OG 5-6 gallon batch (like a Barleywine), or fit a moderate amount of grain (less than 25 lbs) if you were doing a 7-9, maybe 10 gallon lower OG batch (like a session ale).
Was just wondering if I'd be able to squeeze out the occasional 20 gallons of pale ale. current recipe is 20lbs for 10g. Guess that won't work out so well. Or I just mash thick. Friend and I brew together and split 10 gallon batches. Be nice to split a 20 from time to time.
38-40 lbs here. my false bottom sits right at the curve of the bottom of the keg. so its 15 inches in diameter. i did 11 gallons of an imperial stout and got an og of 1.097. would have been higher if it were just a ten gallon batch.
I have a full false bottom and packed 44-15/16 lbs into my A-B half bbl keg MLT for a 12 gal batch of Barleywine. It was .78 qts/lb above the false bottom or .839 if you account for the space under. Took a while to dough in, that's for sure. I wouldn't plan on doing this very often.
36# in mine with about 1 quart/ gal. I do something similar, two of my session ales that have quick turn around and go fast around here I did a sorta "party gile" by using one mash for two boils. Same time for prep but just stagger my boils by 30 min to account for cool time. It's awesome, have been really busy so being able to crank out 20 gal in a brew session really has it's perks.. I really couldn't find anything under any searches I did so I winged it. Works not only in theory.