All you really need is about 200 non-American Eagle brass casings and you should be able to reload those 4 times each. The Federal blue box stuff reloads alright, and the Winchester PP stuff works. Personally I like the PRVI brass, maybe I'm ### or weird but it's rock solid for me.
If you're wanting to blast, remember that bi-metal stuff like MFS and Norinco will wear the chrome lining out of your barrel significantly faster than straight copper jackets, especially if you rapid fire a lot. You will save money by just buying the cheap ammo if blasting is your intention, but if you do get an accurate m305 I wouldn't fire that stuff through it, save it for your cqb rifle builds. The cost of a new barrel is less than buying 308 at $.90 / shot, so don't feel guilty if the gun shoots more than 2 inches at 100 yards with federal blue box 150g.