I am going to be shooting at 1000 yards tomorrow morning for my first time. Rifle is a Remington LSS .300 RUM with the newer VX2 6-18 Target. I have a load already and its my 200g SMK load. I was just wondering though, if I could load up 3 shells each of different lengths say of 3.6", 3.630", and 3.660" to see which is more accurate at 1000 yards? My original load was set at 3.6", but it gave a 4 inch, 3 shot group at 800 yards, then about a 12 inch, 5 shot group at 800 yards with the same shells, just about 2 months later. There is a 27" tv shoot coming up soon and I need to start practicing. I need as much info as I can get.