I had MGM make me a long throated 15 7/8" 45-70 fluted stainless bull barrel with their integrated tactical muzzle brake. The hot loads are just under 3,000 ft/lbs with the Barnes 300gn TTSX. It's a hoot to shoot and very manageable with +p loads, but at your rate, an hour of loading would be many years worth of shooting.
What types of bullets do you like for the 450? The Barnes are pretty $pendy for plinking and the Hornady 300gn interlok hollow points pattern rather than group for me.
For most hunting the 300gr Nosler Partition. I have 4 45-70s and my son has one as well as my .450 rifle so I grabed several when I had a chance. These loads will also be right at 3000ftlbs. I also load the Barnes 300gr TSX. I have some special cast bullets that were actualy designed for the .450 chamber from 420grs to 560grs. If going after another buffalo or such llike those will be the choice. The saami .450 throat actually measures .458" in front of the case mouth where the saami 45-70 measures .450" in front of the case mouth. The early Ruger #1 45-70 was chambered like the .450 so that the 500gr Hornady solid and 510 gr soft point would chamber in on crimped in the crimp groove. Marlin chose to open up the 1895 chamber so the .400gr Hornady 350gr RN could be crimpled in the groove. When the .450 Marlin was born they standardized the .458" throat. In the single shot encore barrel this opens up all kinds of possibilities. One enterprizing mold cutter designed some bullet to take advanctage of this and opened up nearly 10grs of powder capacity which is why I did the .450. I bought the 420gr mold and he also sent me a ton of those bullets.
