bullet velocity v's group size

[mitchellchandler_au]

Hi all,

I was wondering if the approximate velocity spread can be calculated from the size of the vertical spread in the groups. The reason I ask is because most of my groups shot with my 17 pound 6br shows about .750 to 1.000 vertical at 300 yards with the groups running around the 1.000 mark most of the time. So I was wondering if there is a velocity spread problem or is the vertical comming from the fool using the rifle.

Any points of view will be and are most welcome.

 

[Forum Boss]

Some of the vertical you see at 300 is induced by velocity variations, while some of it is just the normal "spread" of group size, which takes bullets away from a perfect center to all points of the compass.

With my 2920 FPS 6BR load,105 Scenars) a 30 FPS ES translates to about 0.1" of velocity-based vertical. 50 FPS ES would be about 0.12",as calculated by Point Blank software).

I would say, however, that some of your vertical at 300 is attributable to the driver and gun handling. Try experimenting with different positions of the gun on the bags, and more/less holding on the rifle. Unless you have a really perfect rifle/bag set-up, a little bit of down pressure on the stock may yield less vertical than shooting pure free recoil.