Mickey - I think you will find that the 'modern' double barreled muzzleloaders are merely put together and Hail Mary if they shoot together. The barrels are generally aligned by lazer to converge at a given range, then brazed together - done deal. Some shoot well, others don't. This goes for .58's through newer 12bores I am sure. Some even had two sets of rear sights, one for each barrel, spaced in the middle rib, and adjustable for windage and elevation. I've a friend with a .58 that puts patched balls together at 100 yds with 120gr. 2F. Most others (I've seen 4) won't put them in the same county using one set of sights. My other buddy has to use both sights, one for each barrel. Luckily for him, the first shot is the furthest sight, so he folds it down for the second shot. The dispersion is crossed, diverging, and has elevation problems as well. Not only that, but the nipples stick way up in the air above the fences, showing improper breeching compared to ANY originals I've seen.
: Colorado's finally got a 12 that shoots well. His first, sent back, crossed with piddling target loads and got worse as the charges were increased.