Velocity, burning effiency, Velocity spreads, std dev. have a significant amout to do with accuracy especially at long ranges. I learned this in the past few years shooting up to 600 yards with my custom 300RUM. At 100 yards I get .5MOA accuracy @100 yards with 200gr matchkings and 91.5gr of H1000 loaded at 3.625COL with Federal Match 215 primers but with velocity spreads of up to 80 to 100fps according to my chrono. When I moved it out to 600 yards, I see the groups stringing vertically. With my 308Win, I don't see this. The FN SPR I use gets consistently 1MOA accuracy at 100 yards, but I get smaller groups with no veritical stringing at 600yards but I have velocity spreads of 20fps. This is with 168gr matchkings and 47gr of Varget with fed 210 primers.