Your 308 with 165 grain bullet will handle a 300 yard shot with ease.
The biggest factors are going to be the environmental factors, wind, rain, etc... and they are big ones in your area. Also the quality of your ammo is a big one.
I use a Swarovski Z6 5-30x50 and it has multiple lines (zero + 50,150, 250, 350 yards) on a calm day with good ammo I can get 2-3 inch groups at 300 yards with my Savage 10. With cheap ammo I can't even get on paper.
Experience is a very bad teacher because it first gives you the test and then teaches you the lesson.