I haven't made up any ball ammo but these are some velocities using factory and reloaded Remington 150gr PSPCL in my 18" barrel.
Remington places their 150gr PSPCL at a muzzle velocity of 2820fps (probably from a 24" barrel). My average with that ammo in an 18" barrel is 2630fps.
Lyman's 50th Edition has data using Hornady's 150gr #3031 which is very close to Remington's bullet design.
Lyman's data with 45.0gr of BL-C(2) produces 2717fps in a 24" barrel. The same charge (with Remington's bullet) produces 2465fps in my 18" barrel.

Hope this gives you some ideas or confirmations!