I did reach out to Hornady. Here is their reply:
"The trim to length that we recommend and use for our 45-70 FTX and MonoFlex loads is 2.040" and we have not pressure tested these loads in cases shorter than that. The C.O.L., when using our 325 grain grain FTX bullet, is 2.590".
The 325 grain FTX bullet has a terminal velocity range from 1300 to 2300, this would be impact velocity; no worries about putting it on the shoulder. At the low end of velocity I would put it on a shoulder rather than through the lungs to help the bullet perform better. The loads you are talking about are within our load data range for H 4198 but again we have not pressure tested in the shorter case."
I was surprised to see the seating depth at 2.59" as I thought normal max was 2.55" for reliable feeding.
