In order to get 35 grs of powder in a 56-50 Spencer, you have to do some compression. I got 30 grs FFFg in using the bullet to compress slightly. The bullets are seated quite deeply into the case as the Spencer action is VERY particular about OAL for function. That applies to the modern pistol calibre versions as well.
You don't shoot a Spencer for power. I've got two Shiloh 50-70s and they smack deer and bear pretty hard. In the day, the Spencer filled the need for a quick firing skirmish gun for cavalry. Minute-of-soldier or horse was all that was expected or required of it, most actions taking place at relatively close range. The stubby 350 gr bullet did not carry well at long range.
The original RF cartridge was simply a slightly longer RF .50 Remington Navy, the 56-50 case miking 1-5/8" versus 1-9/32" for the Navy. They got 45 grs of Musket powder into the Spencer case because they were a balloon headed case, not solid base like today's brass. They undoubtedly had a little more power and range.
I was able to put three rds into a neat cloverleaf offhand at 20m yesterday, despite -12C temp and wearing Mechanix gloves. Two flyers widened it to 3", which I attribute to the trigger pull. They printed 6" above the point of aim, typical of guns of that era. I then shot 5 more rds from a rest into a 2" group and 5 more into the same group off hand, widening it to 2-1/2".
I call that pretty good performance for 1860s technology. Would I taker a deer with it - yes, at no more than 75 yds, but first I want to see how it fares at 50m.
I would have been smart to clean the bore after each five rds, but cleaning under those temps at the range held no appeal. I did pull a Bore Snake thru' the barrel after the initial 5 rds. The barrel had a build up of hard powder fouling near the muzzle and no "lube star" on the crown, indicating insufficient lube on the bullet. I have an Accurate 51-350S mould with a large grease groove, but I'm waiting on handles for it.
This will be a "fun" gun and a sometimes nostalgic gun for CAS. It is NOT a "gamers" gun in that it's "Clink-Clank-Clunk" action requires cocking of the hammer as a separate action. The owner's manual says - "We have found that the Spencer functions best if the lever is moved briskly through the downward and upward travel without hesitation between the downward and upward strokes."
They mean it, as any other action will cause the gun to jam up. It is also hard on bullet noses as you quickly find out with dummy rds and eventually they will hang up, requiring a file to smooth them.
Don't let this discourage you if you have a yen for a Spencer. Like a paper '63 Sharps, you shoot it because you love it and the history behind it. Not only was it a favourite of the US Cavalry during the Civil war and the Indian Wars, Canada bought several during the Fenian fracas.
"Boots and saddles, Troopers!" General Custer awaits.
