Yesterday I tested some loads in my 400 double.
I have been using IMR 4831 and I am doing some tests on RL-15.

71.5gr shoots ok with the 400gr bullets, but I am going to try 72gr next.

The 300gr Hawks did not like 71.5gr at all, so 72 and 72.5 are next for them.

I did shoot some 325gr cast bullets with 44gr of IMR 4198 and 12 gr of poly.
This is a Nitro for Black type of load.
The load shot ok at 50 but I will try 45gr next time.

I also loaded some Sierra 210 HP bullets designed for the 41 Magnum. I used the same 44gr of IMR 4198, with 12 grains of poly. They cut one ragged hole at 50 yards.

I had 6 rounds of 400gr loads left over.
As I already had enough data at 100 yards on them I thought I would try something.
I put up a 16" piece of steel at 300 yards.

I did not have any long range data with me on 40cal 400gr bullets so I just used the SWAG method. [SWAG = Scientific, Wild Assed Guess].

The scope is a S&B 4x. I put the power on 4x and held the steel target halfway between the center cross hair and the start of the bottom thick post.
Using the right bbl which is dead on at 100 yards I fired.
The steel was hit well near the center. The remaining 5 rounds also hit the steel making a nice group.
I have killed a caribou with this double at @150-175 yards with the iron sights, and
I have shot this double on rocks at 300 yards with the flip up leaf with good results, but the key here is, I could not even see the steel plate at 300 yards with my naked eyes.
Between the sun, the color of the plate and the backstop, I could not get a good sight picture with the iron sights.

Whenever I finalize on the final loads for this double, I will due some more distance shooting, side by side with a bolt rifle.

Great report, Tony! My Hollis is due for a scope at the end of this year. Hopefully in time for January.

Very interesting results.

Even though I do not shoot that good your research has changed my thoughts about the limits and uses for a double rifle.

I look forward to more of the information from your trials and experiments.

Wow, that is great shooting!

You know Tony, that is akin to pornography, incest and child molestation. Using a scope on a double rifle is a vile, hideous, thing to do!