I hunt in NW GA, if I will be hunting down by the creek in thick hardwoods I take either a 30-30 or 12ga with slugs (100yrds max).
If I will be hunting the high ground, I prefer a 30-06 or 270 (old school) where a 300yrd shot is possible. I've been using the Remington corelokt bullets for almost 50yrs
If I am hunting from the kitchen table (preferred) I like the 12ga and buckshot.
For your situation wanting 300yrds I feel the 30-30 would fall short if you could shorten that to 150yrds the 30-30 is great.