Bottleneck rifle cartridges and their appropriate powders in 16"+ barrels behave differently than a straight walled pistol cartridge going from one barrel length to another over twice as long.
Go to the Hodgdon online load data. They list 308 Winchester in rifle data and handgun data. IIRC the test barrel length drops from 24" to 15". With the typical 308 powders you won't find any major reshuffling between the barrel lengths.
Your H4895 will be just fine.
