This may be some useful information on loading for the Henry Big Boy Steel .44 magnum. (Side-gate)
Here are tidbits I found with my Big Boy .44 mag., other rifles may vary.
My rifle will generally feed any cast bullet, SWC, RNFN, hp, etc as long as the OAL of the cartridge is 1.64" or less. BUT, crimp grooves are not always located to this measurement.
The Lyman 429421 is entirely too long, as the front driving band would be inside the case, and the crimp would not prevent bullet "setback" in a lever action.
IF, I seat the RCBS 240gr SWC to the 1.64" OAL and crimp on the front driving band, the cartridges will feed perfectly. I realize this is not the optimum way to crimp.
The Lee 429-240-SWC seated to crimp groove feeds perfectly, 1.60". Feeds slick and easy.
Also the Lee 240 grain RN boolit will work if I first "bump" a flat-nose profile on boolit and then load to the crimp groove. This gives a OAL of 1.64".
My barrel mics at .431". I size at .432" Barrel twist is 1 in 20 inches, 12 grooves.
The RCBS and Lee molds are casting about .001" to .002" under .432" (depending on the mold), with ACWW, so I PC, then size to .432". (Gas-check where needed.) Absolutely no leading, barrel cleans with a patch or two.
Groups at 50 yards are 1 1/2" to 2" for five shot average. I get 3" to 4" groups @ 100 yards for 5 shots.
I am using H110 and 2400 powder, and more load development is ahead.
Just an observation, I also have a Winchester 94AE in .44 magnum. It has the solid butt-plate, while the Henry has a generous recoil pad. I can shoot the Henry from a bench all day without any discomfort. The Winchester starts to thump my shoulder after about 30 to 40 rounds. Not extremely painful, but I can feel that "warm glow" in my shoulder with the Winchester after hammering a long string of magnum rounds. The Henry is mild and comfortable because of the recoil pad.
(I don't even want to mention my Marlin 1895 45/70 off the bench!)
Hope this info may be of use for anyone wanting or owning a Henry .44 magnum.