How much does a half grain really matter?

[horseman2]

http://i209.photobucket.com/albums/bb50/horseman23729/260Remington-IncrementalLoads003jpg-1.jpg

http://i209.photobucket.com/albums/bb50/horseman23729/260Remington-IncrementalLoads004jpg-1.jpg

These were groups fired at 200 metres with a powder variation from 38.0 grains of IMR4064 to 41.5 grains. #1 is the 38 and #8 the 41.5 in 0.5 grain increments. The bullet was the 120 brain Berger in a .260 Remington.

 

[horseman2]

http://i209.photobucket.com/albums/bb50/horseman23729/260Remington-IncrementalLoads004jpg.jpg

http://i209.photobucket.com/albums/bb50/horseman23729/260Remington-IncrementalLoads003jpg.jpg

Try these to see if they come up better.

 

[cdn shooter]

http://i209.photobucket.com/albums/bb50/horseman23729/260Remington-IncrementalLoads003jpg-1.jpg

http://i209.photobucket.com/albums/bb50/horseman23729/260Remington-IncrementalLoads004jpg-1.jpg

These were groups fired at 200 metres with a powder variation from 38.0 grains of IMR4064 to 41.5 grains. #1 is the 38 and #8 the 41.5 in 0.5 grain increments. The bullet was the 120 brain Berger in a .260 Remington.

I have had the same results with a Shilen barreled 7mm-08. 3.5" 10 round ladder test at 300m. I was running 44.5 to 47.5gr W760. I have however observed changes in the load with respect to vertical consistency with as little as .2gr change. I only really detail loads to .2 gr if they are going to be shot past 600m.