I can't see why you can't reload 00 buck in a 16ga. shell. As said, you may only get 6 or 7 in rather than 9 balls in the shell, but if it patterns well it should do out to 35 yards or so out of your "tight" choked gun. I would use some kind of "filler" with the load, which should help the patterning. On the other hand, like Drilling Man said, I wouldn't shoot 2 3/4" slug rounds out of your "short" chamber if you value your gun. The method and strength of how the barrels are "attached" vary alot on many "older" combo and drilling guns and I've heard of some of them "shooting" the solder loose (expensive). However, Brennekee slugs are designed to shoot in the European, tightly choked guns and I can attest to the fact they shoot very well indeed in my drilling. I once lived in Virginia and know of some of the areas of which you speak where only "buckshot" is allowed, but I did not know of the "00 restriction; otherwise, I'd use the #1 buck of the factory load, for it still carries twelve (I believe) 25cal round balls that are very "lethal" given the short range "jump" shot" opportunities you might encounter. Jager