Runner: This has all been done, and tried several times over the years. The .45 boys would best pay attention the .45-70 BPR cartirdge fellows, and to the workings of Paul Matthews, who is considered the most knowledgeable source on that cartridge living today. Even the research buried long in the archives of the U.S. Army testing centers have been dug up and gone over to glean some lessons about choosing the correct bullet, length, weight, shape, etc.
Mr. Matthews writes in the Single Shot Exchange, as well as has a couple of books still in print on that cartridge. You can save a lot of time and frustration reading all the research others have done since 1873. The BPC guys are shooting round nose, 535 gr. bullets for long range shooting with their .45-70s, and .45-90s. A long match is pretty brutal with those loads, and that is why so many are playing around now with the .40 caliber cartridges, as you get better BC, in a lighter weight bullet, that shoots flatter, and may be blown less far by the winds. The recoil saved is also worth the effort, and the .40-65, and the .40-70 bottle neck cartridges are getting new life. I even saw where someone is shooting a sharpes with a .40-82 cartridge to make it an " express gun ". But, pointed bullets are not going to do it. The round nose bullets are the way to go for accuracy at long range.
Now, if someone goes down to the .38 caliber BP cartridges, and makes a really long bullet with a pointed nose, they might get it going fast enough to make used of that design. Wind drift has always been the killer on the smaller caliber bullets.