So I own a Epiphone Jack Casady bass that came with a gauge of 50-75-85-105 strings.I want to switch them out for some flats but dont want to setup the bass(due its already setup) and was wondering if a 50-70-85-105 gauge string would work
With that in mind, you'd better not change those strings, probably forever. Cause, even if you have changed them with other 50-75-85-105 roundwounds (assumed rounds came with your Epi), still there are chances your bass would need to be re-setup.
Flats are usually higher tension, If you don't want to mess with setup, ask around for recommendation of Setup tech in your area.