.692 is generally 14 bore, not 16, BTW. .662 is 16 bore, of course, groove diameters will vary slightly. I'd expect a 16 to be no more than .675 on the grooves.
: Pure lead or perhaps 30:1 or 40:1 lead to tin would work just fine. It is also a solf alloy.
; I have used 1/2 and 1/2, pure lead mixed with WheelWeight metal to good advantage, even in smaller calibre BP ctgs guns, saving somewhat on my meager pure lead stocks suplimenting it with free wheelweights.