I've used the three-ball load in my own 1895 Marlin with 22" barrel.
I put 10 grs. of Unique in a primed, sized case, that had been belled to avoid shaving the balls (okay .. okay ... let's all have a little giggle over "three balls" and "shaving the balls" then get over it and move on ... ).
Enny-wayyyyy ...
A Speer .457 inch lead ball was seated an inch down or so. Then an Ox-Yoke Wonder Wad of .45-caliber was placed over the ball.
Then another ball seated on top of that seated wad. Another wad over it. Then the third ball on top of that wad.
The seating stem of the die was run down as far as it would go. With a little careful experimentation I was able to seat the top ball to where it was seated with the circumference slightly below the mouth of the case.
Of course, seating the ball thus pushed the other balls and wads down. It is important to know that there must NOT be any space between balls and wads.
With the third ball seated with the circumference slightly below the case mouth, this leaves an open area twixt the ball and inner case. In this area, lubricant may be smeared by hand, or melted and gently poured in.
I used scrap bullet lube of Alox composition, smeared in this space. To my notion, it's easier and less messy than melting and pouring.
Shooting this load at 100 yards is a waste of time.
It's not intended to be a 100-yard or even 50-yard load. I have only fired it at 25 yards, where the balls typically stay in a palm-sized group.
If you can get slightly larger lead balls, then do so. A lead ball of .459 inch would be about right but I don't have such a mould and the Speer .457 inch ball was readily available.
This load is NOT intended for the Trapdoor Springfield or firearms of similar weakness.
Three balls, with two wads and lubricant, weigh close to 450 grs.
The Lyman No. 47 reloading book (copyright 1998) lists a Lyman cast bullet of 420 grs. with a starting load of 11 grs. of Unique, in the Marlin rifle, for a velocity of 1,006 feet per second (fps) and a pressure of 16,800 Copper Units of Pressure (CUP).
I WOULD NOT recommend this load in any deringer or similar arm. If you use it in one, you do so at your own risk (and are your eyes and hands worth the risk?).
With this as a guide, and the reduction of the charge to 10 grs., the load has been safe in my circa 1977 1895 Marlin. Whether it's safe in your rifle is another matter. I assume no responsibility for you using this load.
This 16,8000 CUP pressure level exceeds that recommended for the 1873 Springfield, original and reproductions, but it's considered safe in the Marlin.
Velocity of the three balls is tricky to figure, since the three balls confuse the chronograph. It's likely around 1,000 fps as well.
I cobbled together this load some years ago to play a prank on a friend, who had never before fired a rifle larger than a .22 rimfire.
We set up a 9" paper plate at 25 yards and I loaded the rifle. He expected a lot of recoil and was (of course) pleasantly surprised to find it was quite mild.
When we walked up to look at the target, after three shots, nine holes stared back at him.
His mystified look was priceless.
I chastized him with, "What the heck are you doing?"
He was speechless. He swore that all he was doing was aiming and pulling the trigger.
I feigned disbelief and said he MUST be doing something wrong and began quizzing him on his sight alignment until my laughter exposed the gag.
Later, we tried some regular loads with a 420 gr. lead bullet at about 1,500 fps. He was impressed with the Marlin's recoil then.
The three-ball load doesn't really have much use.
It's not accurate enough to knock off rabbits and grouse (usually, you want to take off their head with a precise shot; a .45-caliber ball would likely tear up too much eating meat) and the balls are too destructive and carry too far to dispatch pests in the barn or near housing areas.
It's strictly a "gee-whiz" type of round that's fun to shoot.
At one time, I had my Marlin 1895 loaded with four of these cartridges as a house defense gun. It might have such an application for close-range defense where stopping power but not penetration are needed.
However, a judge would probably have a field day with these rounds at your inquest.
I soon adopted a pump 20-gauge shotgun loaded with No. 3 buckshot as my house defense gun and shot the last of the three-ball loads a few years ago.
I don't know that I'd ever make up more cartridges, unless it was to play another prank. The loads's range and usefulness are very limited.