Start at about 103 grs. of IMR-4831 and see where it shoots..You have to find its regulation load...You can go up to about 108 grs. from there. I personally wouldn't go above 108 grs and thats usually 2245 FPS and kicks like a mule..Load up 4 or 8 each 103, 104, 105, 106, 107 and 108 and head for the range and shoot them until you get a tight group...
Better yet, but seems to complicate some folks is to shoot them until the first two shots cross each other then back up until they do not cross, keeping in mind that if they are too far apart then UP the load until the groups come together, if they cross each other back off about a grain or two. YOu goal is to make them come together as close as possible without crossing..be sure and have a pad on the bench to number your shot as rt. barrel and lft. barrel. Don't flinch or your toast.:)
To know your goal, before you do the above, you must first shoot a couple of groups with EACH individual barrel and find out which side shoots the WORST and that is the best you can expect from your double rifle as to accuracy, therefore that will be your goal with both barrels..A double will only shoot as well as its WORST barrel...After you have determined your best group, fire a few groups to varify it..then sight it in at 50 or 75 yards. I personally like 75 yards.
The load that I have hunted with the most is 85 grs. of RL-15 and 5 grs. of dacron with both Woodleigh softs and solids, it usually shoots them together in most rifles btw..recoil is very mild for a .470 and it kills buffalo exceptionally well at 2020 FPS...It also has a tendency to shoot to the same POI as my IMR-4831 regular loads for some reason that I do not completely understand but then understanding a double rifle is a oxymoran anyway, they just do what they do
