The 45-100

[bruce moulds]

jim,
you give the 45/2.6" case its correct nomenclature when you add the number 100.
the 45/2.4" case was also 45/100. not as it is so often called today the 45/90.
the 2.6" case came first, with the intent to use what was considered the ideal charge of 100 gns .
it was soon discovered that the more bullet in the barrel and the less in the case, the better the accuracy.
shortening the 2.6" case to 2.4" allowed 100 gns to fit with a bullet barely in the case, same cartridge overall length.
of course a natural progression from this would have been to seat the bullet right out of the case as in breech seating.
once breech seating became popular, people wanted more, and went back to the 2.6" case, droptubing it full with 112 to 115 gns of powder and about a 1/8" gap between the base of the bullet and the wad level with the top of the neck.
such ammo was shot up until about 1912 at sea girt range.
which leaves the 2 7/8 case.
it was only ever loaded with 110 gns with a really light bullet, totally unsuited to most uses.
in fact it was the only 45/90 sharps cartridge when loaded with sensible bullets.
the shallow seating of the 2.4" case for target use was great in that application, but totally unsuited to hunting.
the 2 7/8" case would run 90 to 100 gns of powder with deep seated mostly 500 gn bullets, and cartridge overall length was usually less the the 2.4" case loaded with a 550 gn long range bullet.
with regards modern cases, which are thicker than the old balloon head ones, fired 2.4" cases will take 100 gns of swiss 1.5 or 1.0 droptubed, and then a thin was as well.
compress this about 1/10" or 1/8" and you have a good pp load. or just leave the charge as is and breech seat the bullet.
the 2.6" case will take more loaded similarly.
modern users of the 2.6" I believe include dave gullo. this could be open to correction.

keep safe,
bruce.