I had a Browning low wall in 45 Colt a couple years ago. It had a tang sight but was not drilled and tapped for a scope. I shot a variety of ammo. According to the range notes that I recorded at the time, Hornady FTX and American Eagle both shot very well (under 1") at 50 yards. That was great shooting for me with open sights. Not being able to mount a scope was the only reason I parted with that rifle.
Most .45 Colt factory ammo is loaded very weak in deference to the old firearms in that caliber. Hand loading (or Buffalo Bore ammo) will get you very close to .44 mag velocity.
