After having good results with full power loads with IMR3031 and IMR4831, but hearing of possible problems I worked up loads with RL-15. When I tested the loads at 100 yards 89grains of RL-15 with 480 Woodleigh's soft and solid both hit about 5 inches low.
89gr. shot just @ 2"to 3" low with Hornady soft's with the softs in the left bbl an inch or 2 lower. The Hornady Solids old style shot good near poa.
88gr with the 500gr. Swift A-Frame hit spot on.
This was my first firing with the Swift so I started with 88gr.
Thinking that reducing the rounds that hit low by one grain of powder might give them "more barrel time" and cause them to hit higher on the target I repeated the test with 88gr of RL-15, [with a foam filler] for all the above bullets.

All shots kneeling, no artificial support, at 100yds, with 88gr. of RL-15, Bertram cases. My rifle is regulated for 75gr. Cordite 480gr bullet max and so marked. This is the so called "Tropical Load" the regular load is 80 gr. Cordite.
The 500gr Swift A Frames shoot very tight and to the point of aim. This may be my best shooting load in this rifle.
The 500gr Hornady softs moved up to an inch or two low with the left bbl shots comming to overlap the right bbl.
The Hornady 500gr. solids, Old style, shot good but I think the 89gr. load is a little better.
The 480 Woodleigh soft's moved up to impact about 2 inches low and the left/right impacts overlap.
The 480gr Woodleigh solids hit about 2 inches low and the right and left bbl shots overlap.
Shots with the 480 Woodleigh softs from the left and right bbl hit into one ragged hole at 35 yards.

All shots were fired on two different deer targets as to keep the right and left bbl hits seperate. The right bbl was always fired first, next test I will shot the left bbl first and see if it makes a difference in this rifle .Usually I fired a right/left, reload and a right/left, checked the target and let the rifle cool.
So, It seems that my plan has worked. This will be reconfirmed at my next trip to the lease.

The New Style Hornady 500gr. solids with the Brass Jacket are wild as a March Hare in this rifle with 88 or 89 gr of RL-15. Both bbls shoot 8 to 10 inches low and 6 inches left.88gr shot slightly higher, but still way left.

I e-mailed Geoff at Woodleigh about the 500gr Woodleigh's. He replied that the 500gr have the same jacket construction and would preform the same as the 480's. My rifle seems to shoot 500 gr. bullet better so I may try some 500gr Woodleigh's in soft and solid, However the 480's shot plenty good enough to hunt with.
I hope not to take a shot in Africa over 35 yards as I like to get close , but I always want to know where my rifle hits at the longest range I would feel comfortable taking a shot at. I have killed deer with this 450 No2 at 85 yards with the Hornady 350 RN and 81 gr. of IMR 3031, with filler of course. These loads hit poa at 100 yards,vel @ 2300fps.

Have you other double shooters noticed a rise in impact at 100 yards when you reduce your powder charge. I am going to shoot a pig with the Swift A-Frame. I will either hit him through both shoulders, or shoot him head on, to better check bullet expansion.

If it don't doo good I can always sue Swift as I bought these bullets directly from the hands of the owners.
He also said the A-frame should still give some expansion at 1600fps.

450#2

You raise an interesting point in that you can raise the POI by backing off of the load at times. Most people do not know this or don't believe it. Well done.

Are you using filler and what type?

With 3031 and 4831 I have used both polyester pillow stuffing[dacron] and foam plugs cut out with a sharpened 50 BMG case. With RL_15 I have used only the foam. I much prefer the foam, as you do not have to weigh it, you can cut it out ahead of time, and it does not leave large tufts of white pillow stuffing all over the ground. I have used a "soft" grey foam and a "denser" black foam and can tell no difference. The foam is compressed against the powder by the seating of the bullet. Upon firing the foam is found about 5 or 6 yards in front of the muzzle. You can see rifling marks on the foam and it is torn in about half, not burned as I have marked the end against the powder, it is not burned. The dacron is not burned either. I use Federal 125 primers.
The 450 No2 case is so large that I get hang fires even with 100gr.IMR4831 without filler.
I do not know where all this "stuff" about doubles being hard to find loads for, I have had no problems with different powders or different bullets in the 3 I load for.