Redhawk: Ill vouch for the practicality of the .45-2.4 It has more than enough steam for 1000 yd shooting, but it may be a bit overkill, esp. in a lighter/carry rifle for silhouettes. While the .45-2.1 is a great cartridge, I feel the .45-2.4 is the great all-around BP .45 cartridge!
From my experience, it is a very versatile caliber loaded either w/ BP or Nitro/White Powder (AKA smokeless) as the case is not that cavernous so as to loose the powder charge. Id say it is bout the longest .45 BP case that Id care to load w/ Nitro/White powder.
I also have a Sharps-Borchardt in .45- 2 7/8 (AKA .45-110). Even thought it is almost a 14# rifle, when loaded w/ a 100 grn BP & 545 grn Paul John Creedmoor bullet, it does get your attention when it is touched off. Under certain condition, the lube can fail. Ive had to happen to me. On hot day, w/ not enough time in between shots or not cleaning in-between shots, the lube will fail in the Borchardts 34 barrel. Of course this is my fault, not really the rifles or the load. Since I dont shoot competition anymore, I usually wipe between shots. (I also really need to get serious & develop a gilt-edge accuracy load for my rifles.)
Both calibers will knock down anything on 4 legs (or 2 depending on the circumstances) in No. America.
If you go w/ a .45- 27/8" definitely get the heaviest rifle for the intended purpose. Too heavy a rifle will be cumbersome afield. If shooting @ paper targets, I'd go w/ the LR BPCR weight limit.
Ive heard it said that the .45- 27/8 has a steep learning curve, esp if youre a tyro BP shooter. I can readily believe it. If you are more experienced, the curve is not as steep, but it is still there.