I hunted with a .50 Cal for 30 years with a 90 grain charge and all too often I got no exit wound and I was left tracking deer with little to no blood trail. Once I moved up to a .54 with a 90 grain charge all that ended. and I never looked back I diss the N-SSA because they don't use original service loads and other things like drilled sights. They have no respect for history.
90g in a 50cal is way more than needed but, if your gun could group with that, then it's all good. By moving up to a 54cal with the same charge, you've effectively lowered your charge level by increasing the bore size. I've seen more than one 54 shoot rather well with 90gr.
As for the "service charge" thing. What most don't take into account here is the quality and makeup of the powder then v now. Without testing to confirm the energy/gr of any given grain size of original powder v modern makes any "historic" comparison pretty much meaningless. The best we can hope for is an approximation. Also remember that 45g 3f Swiss is every bit as hot as about 50g 2f Goex without the same level of fouling. So is 10g under the "service charge" a "mouse fart" if both the modern powders yield very close MV to an original per ordnance records? It is a very well known fact among serious shooters that nodal points are absolutely where accuracy occurs and with that in mind, every combination of powder, cap, lube will yield different results because they all have different vibration patterns hence, nodes. True, some in the N-SSA use very light loads but many, me included, use loads that do have some recoil but all that is based on accuracy. Some older folks don't like tons of recoil and given the amount we shoot at a match, recoil can begin to work on your accuracy quickly and there's no reason to induce flinching if you don't have to.
But back to original v modern reprop, just because the "original" minies were .575 doesn't mean they worked in production rifles of the period because tolerances from the lowest bidder vary quite a bit so some rifles shot well with .575 and others would be hopeless. By taking that variable into account you can get very good accuracy just by adjusting the size of the bullet to function as Minie designed it. For those wanting an authentic experience with "service" ammunition, go ahead, but don't expect anything like usable accuracy unless it just happens by chance. Even in modern service rifle matches, if allowed by the rules, competitors will NOT be shooting "service" ammunition. It will be custom tailored to the rifle for utmost accuracy and is often under the "service charge". So are they shooting "mouse farts"?
I learned long ago that "more power" doesn't always equate to accuracy. One of my friends back in the day was all about power and how much powder he could get in a cartridge without blowing it up. At the range, in inpromtu matches, I'd thrash him almost every time with my ammo that was tailored to the gun.
A true "mouse fart" load I've seen is pretty much most Cowboy Action ammo. That's a speed competition shot at close range and accuracy isn't nearly the premium it is in N-SSA or other matches shot at distance.
What Malachi said except I'm pretty sure that barrel is going to have a round ball twist.
