trying to make sense of 6.5-284 brass

[Joe R]

fastarget said:
Have had inconsistent loads mostly. Powder measured to .02, brass prepped the same each time, still will get 4.0 SD one day, 12.5 SD the next day, same ambient temps etc. Neck tension set with a redding die and bushing to obtain .002 tension. Chrono will read for example 2982, 2986, 2983,2989, then 3015!!!
Been trying 4350, but now will try 4831c, however It makes no sense it is the powder.

I'm having the same problem with my .308 suddenly getting a round that goes 20-30 fps faster without any reason. I'm pretty diligent in my brass prep and reloading. The only variable I'm not considering is case volume. I've come to the conclusion that, if there is no difference on the target, chrono's make mistakes too. So I've started disregarding it if there is only outlier in the group. YMMV.

Joe

 

[fastarget]

Hi Joe
Thanks for the input. Yes I looked at case volume but the differences there were not significant. I have been turning the old brass and have dome new on the way. Neck thickness on this brass is all over the place. I can feel difference using the expending mandrel. The difference in velocity was affecting my vertical, tested at 600 yds

Also I am attempting to uniform the neck thickness as much as I could going into the shoulder, most are much thicker there and may be causing the firm Closure of the bolt, it was leaving rub marks on the head stamp prior to firing. I plan to shoot a few tomorrow.