Terminology seems to be causing confusion. There is case length (head to mouth) and there Cartridge (not case) Overall Length (COL, often abbreviated COAL or OAL, even though the word "overall" has been a compound word since Chaucer's time, and thus needs only the "O" for its initial).
My drawings show the 7.5x55 case has a 55.6 mm maximum length. That is 2.189" maximum length. Standard practice at SAAMI is to give a tolerance of +0.00 and -0.020" for case length. Most trimmers are set to go right into the middle of that range to avoid going over those limits, so most will be set to 2.179" average trim length, but anything from 2.169" to 2.189" long is considered to be within loading specifications.
The COL I have for this cartridge to ensure magazine compatibility is 77.7 mm or 3.059".
I got my dimensions from QuickLOAD, then checked the in the Hornady manual, and it agrees with the above numbers.
Keep in mind the maximum COL is just for bullets that reach it. I note that Hornady uses a 2.820" COL with their 150 grain FMJ boattail because that is the length you will get when its cannelure is level with the case mouth for crimping. The shorter length doesn't hurt anything. The manual shows 36.3 to 44.6 grains of H4895. That translates to 35.8 to 44.0 grains of IMR4895 based on QuickLOAD's powder database. Your load is in the middle, but higher than the starting load. I don't know how the PP (or sometimes PPU) case volume compares the the volume of the Norma case used in Hornady's testing, so my sense of caution says go to that lower starting load and work up, watching for
pressure signs.
