I can decently answer most questions if your using black powder and casting your own bullets
I'm thinking of starting with black powder or substitutes (I have a few lbs of Goex FFF, a lb of FF, and about 7 lbs of APP. I use APP in 38 SPCL and in 45 Colt in my Cowboy Action matches, but about half the time I shoot smokeless. They have "Long Range" competitions in Wartrace TN once a month, but the range is only 200 yards. I'll probably get a lot of advice from those folks.
I bought the gun sight unseen at an online estate auction, along with 61 rounds of handloads. The previous owner kept pretty good notes on the cartridge box of the ammo, including sight settings from 100 yrds out to 450 yrds. Unfortunately some of the notes are semi-shorthand and hard to read. I know the ammo was loaded with 300 gr cast spire point bullets, but I don't know the diameter nor the mold number. The powder is IMR 4198, but the charge amount isn't listed. The cases are nickel plated Starline 40-65, and have been loaded 11 times. I'm going to pull one of the bullets and mike the bullet and weigh the charge.
The rifle's date code shows it was made in 1997, but their isn't a scratch on it and absolutely no rust. Well oiled inside and out.
This is going to be an entertaining adventure.