1 cases ; yes they can make a huge differance .In my 06' an aquired 150 rnds of what I was told was 1 lot shot 3 separate groups about 8" apart . .2 grains of water differance in case cap. Best example Fiocci load 9900 same load in a Federal case 13500 .

2 Primers NEVER substitute a MAG for a standard in a load that is worked up or even close to max . Best example Win 209 replaced with a Federal 209a 3000 psi . Thats alot in a shotgun that is maxed out at 15000 .

3 I load a minmum of 5 rnds I start low and go up 1 grn inciments and shoot the top down . When the group gets to MY min or smaller I workup .2 at a time . I have 3 pet powders in my rifles and 3 for my shotguns 2 for my pistols . I shoot Unique in all 3 .

4 If you have a known factory load that works well start with those bullets and brass .