First of all, I want to thank the late John Kort, Ed Harris, and Savvy Jack for their posts on this and other forums about loading black powder in .44-40. When I started loading .44 WCF in 2016, they provided the map to success.
I load the cartridge for several replicas: a Cimarron 1873 Sporting Rifle, a Cimarron 1860 Henry Military Model, an Uberti Bisley, and a Cimarron Model P with a black powder style frame. (The Cimarrons are all Uberti-made.)
After I got the Henry I wanted to experience what it would be like to shoot and original with .44 Henry Flat rounds. The original rimfire used a 200 - 216 grain bullet on top of 26 - 26 grains of black powder. Just putting a lighter charge of BP in the larger .44 WCF case is a no-go, because air space can be dangerous.
So, my recipe for .44 Henry-equivalents was as follows:
Federal or CCI LPP
1.9cc* (about 28 grains) of Goex or Swiss 3Fg black powder
0.5cc of cornmeal to take up the air space
219 grain bullet cast from an Accurate 43-215C mold (John Kort's design). The bullets are cast from 1:20 alloy, lubed with a 50/50 mix of beeswax and mutton tallow, and sized to .429.
* Measured in Lee dippers.
This worked very well. Recoil in the heavy Henry was about like a .22, and both noise and fouling were a bit less than my full charge loads with 2.2ccs of BP. I never tested them for accuracy off a bench but ringing a ~10" gong offhand from 50 yards wasn't a problem.
However, measuring out the cornmeal was tedious and I always seemed to spill a bit and make a mess on my workbench.
I found an easier option for a filler in the form of 1/8" thick .430 diameter over-powder card wads by Circle Fly, purchased from Track of the Wolf. As of today, they run $11.99 per thousand.
The card wads are much quicker and cleaner to insert in the case mouths than trying to carefully funnel cornmeal into the cases. Performance has been the same as the loads with cornmeal.
Aside from their use in rifles they work very well and shoot accurately in my revolvers. In the wheelguns they are noticeably more pleasant to shoot than full BP loads, with much less recoil. There is still plenty of blast and smoke, however. Apparently in the late 19th/early 20th Centuries, UMC offered a similar load, probably for use in handguns.
--- Dave Markowitz