Re: Make of brass..
you can do a lot with reg. commerical brass and military brass to get excellent performance. It all depends on the application. If you are BR shooting and have the right equipment, then spend the money and get some lapua brass.
If developing loads for your off the rack hunting rifle, any commercial brass can be made to shoot better then the accuracy of the rifle.
Make sure you get them from the same lot. Do the necessary prep work and check the case volumes after they have been fired. Cull any that show distortions, cause flyers, or have varied volumes. This would apply to any brass you buy.
I have used Lake City brass in my '06 and it shoots sub MOA out past 500yds. The rifle will not do much better. I have used Cdn Nato 308 brass to shoot my smallest group at 250yds (3 shots overlapping). I have also used brass from Win, Fed, and Rem. that shoots 1/2 MOA or better in a variety of prod and rechambered rifles.
The big issues are your ability to size the brass so it is concentric and fits your chamber closely. Seating the bullets straight and in proper relation to your throat and leade makes a huge difference. Of course, using accurate bullets is a must. Lapua brass and 147gr FMJ from your surplus dealer is not going to impress.
Powder & primer choice, bullet quality, and improper loading can all affect your accuracy to several MOA at long range. I doubt a SAAMI chamber will be affected much over 1/4MOA by "bad" brass used with good loads.
Scope parallax will be a bigger issue!!!
For a hunting rifle, even a LR one, save your money and apply to better dies, scopes, bullets, and components for practising. You only need 3/4MOA to be effective out to 1000yds. Well prepped commerical brass will do better then that.