Well, OK. If you are seriously considering concealing a 12" Buntline then I believe you willneed something other than a belt scabbard. I believe you will need something similar to a pocket holster that goes through the inside of the pocket and down along yer leg....
When we/I was in the southeast of the Asia or the Lah-teen of America, we could pack a Tokarev or a Walther, or even a 6 shot Colt snubbie in the flare holder pocket that was inside our cargo pockets on our fatique pants. I beleive the flare pocket was about 8" deep, so if you carry that on through the pants leg to the inside and sew on a 4 or 5" deeper pocket you should have it covered, so to speak... and, it would be quite handly as well, and doesn't print.... a bit of a trip to the seamstress and you should be set......