Ordinary .45 Colt factory loads fired from a short-barrel carbine at transonic velocity give more than ample energy and penetration. Heavier flat-nosed bullets having a meplat of 0.6 to 0.7 of the bullet diameter do somewhat better, but as the graphs below show there is very little difference. The original 1873 40-grain blackpowder service load used before adoption of the Schofield revolver, necessitating a lower 28-grain charge, was known to shoot through a galloping pony to kill the "dog soldier" on the other side.
Larry Gibson pressure tested for me .45 Colt loads with 7.5 grains of Bullseye firing 255-295 grain bullets. I use these in several Colt SA and New Service revolvers, approximating the "full charge" 40-grain black powder velocity with smokeless powder in modern solid-head cases. Pressures slightly exceed SAAMI MAP, but are well within safe design limits of post-1920 Colt SA and New Service revolvers, modern Italian clones and medium-frame Ruger flat-tops. Pressure approximates the .45 ACP about 18,000 psi.
Accurate 45-290H has a long nose to fit Ruger revolvers. It exceeds the cylinder length of older Colts on purpose.
The 45-264H has a nose length to fit Colt SA, and New Service cylinders with full-diameter, parallel-sided forepart which can be sized to fit cylinder throats exactly! It is intended as a "maximum effort" field load for older guns with 7.5 grains of Bullseye.
I use the same loads in a .45 Colt carbine. At woods ranges inside about 100 yards these are stone killers which shoot clear through deer on raking and even Texas Heart Shots, and you can eat right up to the bullet hole with little bloodshot meat. Graphs based upon MacPherson's WTI model and drawings of example bullets of similar shape are shown below.
Accurate 45-255O closely resembles the shape of traditional .45 Colt lead conicals, with the addition of a crimp groove on the ogive, which is necessary when loading for tubular magazine rifles with smokeless powder, to prevent compression of the magazine spring from driving the bullet deeper into the case. This is because modern smokeless loads in .45 Colt do not fill the case, and therefore cannot provide "base support" for the bullet as a compressed charge of black powder would.