the subject of "45/100" deserves some discussion.
when sharps went to 45 cal, and dropped 44 cal except for special order, they quickly came up with 4 chamberings, all called 45/100.
these were 45/100/2.6", 45/100/2.4", and 45/100/2 7/8".
the 2.6" was designed for long range target shooting, but was quickly replaced by the 2.4" when it was discovered that the shorter case was more accurate.
this was because the bore diameter paper patch bullets had more bullet in the barrel and less in the case with the 2.4"
such ammunition was unsuitable for hunting as the bullets could easily fall out of the cases.
hence the 2 7/8" case with the same charge.
the 2 7/8" case was also loaded with a bullet about 200 gns express loading, and 110 gns powder, and in modern times is usually referred to as the 45/110 incorrectly.
modern practice of using grease groove bullets has relegated the 2.4" to a max of 90 gns powder due to deep seated bullets, and is now incorrectly called 45/90.
how people forget history!!!!! for convenience of marketing.
one would guess on this basis that the op is referring to the 2.6" case.
for reference, the 458 win mag is 2.5".
one would assume that the 2 7/8" case loaded to full potential with smokeless would have serious ballistics in a strong rifle.
do not use a cast ballard for this!
I have spoken to 2 guys about their trips to Africa, one using a 2 7/8" and the other using a 2 7/8" and then a 2.4" (45/70) with black powder.
their cast bullets did well, but they are both exceptional shots.
the thing with black powder is that velocities are low enough to not cause over expansion with normal loads and bullets hardened with tin.
the so called 45/120 has a 3 1/4" case, and there is some doubt as to whether it was ever offered by sharps.
in fact it could never have been used in the great bison carnage, as it came out too late.
modern day americans report full pass throughs on American bison with cast bullets and black powder.
starline and norma make good strong brass from 2.4" up to 3 1/4", although both do not do all.
the norma 2 7/8" brass is a little long, so that cases can be trimmed to exact chamber length - a good thing for cast bullets.
my 45/2.4" chamber is of diameter for groove diameter bullets.
the norma 3 1/4 brass shortened to 2.4 " becomes thick necked brass, and can be used in the same chamber for bore diameter bullets.
with black powder these bullets bump up into the rifling, and are as accurate or more so than grove diameter bullets.
with no grease grooves they have less drag than a greaser, and so less wind deflection at 1000 yds.
bruce.