NOW I know.
90 calber Handgonne - one cap full of Goex FFFg and on half a slice of old bread for packing. (Powder chamber of 1/2" diameter about 1-1/2" deep.)
Good deep bang. Several neighbors in full knowledge and participation!
An then the Little gonne - 20 ga 2" barrel on top of 1/2x1/2 powder chamber. Took about 1/2 to 3/4 of a cap full of FFFg and filled 1-1/2" of the 2" bore with bread. Good, but smaller ka-boom.
