Frederik Badenhorst:
Let me caveat this discussion by stating up-front that every rifle will perform slightly differently based on barrel length, ammunition lot, condition of the rifle, and (probably) some sort of voodoo which is only known to the Hunting Gods and which we mere mortals are destined never to fully understand.
The short answer is that during load development for my own double rifle, the load which came closest to the factory data consisted of a 400grain Woodleigh soft over 64.0 grains of Reloder-15 with a Kynoch foam wad filler.
Please note that the Hornady Handbook of Cartridge Reloading (10th Edition) lists this as the maximum load for this powder and bullet weight (albeit with the Hornady DGX bullet). So exercise due caution and work up your loads accordingly.
A more expansive answer is as follows: The data on a current box of Hornady cartridges loaded with the DGX bullet is listed as 2050 feet per second (fps). This corresponds to a load of 64.0 gr Reloder-15 in their reloading manual. As mentioned, this is also (in their manual)
the maximum load. There are several other loads listed at 2050 fps (using H4350, IMR4831, Reloder-19, Norma MRP, H4831, IMR 7828, VIHT N-165, and H1000 powders respectively), most of which are also at or near the maximum listed load. There is no mention of any fillers. It does recommend to
“crimp the case mouth tightly on the cannelure as this will aid in ignition and help provide consistent performance.”
Because Hornady is the only major manufacturer for ammunition available in the present-day, my initial load development began with the Hornady factory DGX load in order to establish a baseline of sorts. The Hornady manual states that the velocities were measured from a 24” barrel (rifle unlisted, although probably a Ruger #1). My double, a 1908-vintage Jeffery boxlock with 24” barrels, was regulated for the old Kynoch tropical load of 400gr bullet over 55 grains of cordite. Notwithstanding the Hornady reloading manual’s claims, three Right-Left pairs (six total shots) of Hornady factory ammunition produced the somewhat lower average muzzle velocity of 1997.7 fps, with a Standard Deviation (SD) of 22.72 and Extreme Spread (ES) of 66.57 fps when fired from my rifle.
I used a reload ladder consisting of 62, 63, and 64 gr Reloder-15 under a 400gr Woodleigh Soft Point, with the aforementioned Kynoch wad. The closest match to the factory ammunition’s performance was the 64.0 gr load, which produced an average of 1990.35 fps. The SD was 11.91 and the ES was 31.02 fps. So from my rifle, this came closest to matching the Hornady factory load, while substituting the 400gr Woodeigh soft for the Hornady DGX bullet.
Unfortunately, neither the factory load nor the equivalent reload regulated acceptably in my rifle, so I did not further pursue that particular component combination. After some tinkering, I eventually discovered a combination which regulated much more acceptably in my rifle by loading the 400gr Woodleigh SP over 63.0gr Reloader-15, separated by a Kynoch foam filler. That load measured 1959.15 fps for three pairs, with an SD of 16.76 and ES of 41.00 fps.
Interestingly, using some of the remaining 400gr Hornady DGX bullets with that exact same powder charge produced an average of 1983.46 fps with an SD of 15.96 and ES of 36.86 fps. The aggregate group opened up some, but it is an acceptable practice load, allowing conservation of my remaining Woodleighs.
Your rifle will of course, be different but hopefully this provides some useful starting data. Congratulations on the new double and best of luck with your efforts!
The final Woodleigh load:
View attachment 639990
Same load but with Hornady DGX bullets:
View attachment 639991
