Hmm - 1 in 42" makes me think it's rifled for a short slug. If possible, you could make a swage and draw the .690's or a .700" down to .683", giving a proper length for the gun.

As-is, the .690's if they don't lead, should be ok as-is, due to the fit in the 'throat' that will be there with short brass.

Your loads look about identical to my 14 bores loaded for the Husky's 13 bore barrel(.703" grooved diameter) with, in my case, a .684" ball. They only engrave a few though, but with straight rifling, work just fine. The mould I have is Italian - maybe Pedersoli and would be the perfect size for your rifle. In Pure lead, they run 480gr. and in WW, a mere 466gr. Quite the moose thumpers they are, too(from my single 14 bore rifle).

Working with these thumpers is sure a lot of fun - and a lot of gun! 160gr., almost 6 drams is a healthy charge and about the same as I use in my muzzleloading 14 bore rifle. They are very accurate at longer ranges, from 50 yards on out to 300 meters and are very consistant as well.

Was out shooting with a fellow the other day - bed his new Rem. '06 for him - first target was poor, with his handload (first for him) as well as 180gr. Silvertips, not so hot. I asked him if I could fire a couple on his first target and he said 'go ahead, you can shoot at it". Well, the first one went just over the bull where I expected it, and second cut the first - perfect! He was suitably impresssed - and amazed. His '06 has a 5-15X scope and he was using double bags, while I held the gun as if shooting offhand, only resting the back of my left hand on the bench rest. This is typical accuracy from this rifle over the past 12 years (built in Spring '86).

With factory Fed. Fusions and TSX's his '06 printed 3/4" and 3/8" respectively for 5 shots, me shooting. He then put 3 into 1 1/4" at 200 meters - good load for that rifle. Couldn't be better, actually. i was tickled it worked with his favourite loads. Prior, it was doing over an inch with both.

With work, yours 16 will do as well as my single. Maybe not both barrels into the same group, but it has the potential to put each tube into similar groups - hopefully paralell. My rifle usually shoots 1.2" to 1.5" for 5 at 100 meters. It has Express-type sights.