My SD numbers are horrible

[silvery37]

I am using an AR platform with a 16'' noveske barrel. My brass is .223 winchester cut and formed to .300 whisper. Using 9.4 grains of H110 under a 220 smk my SD was 55 with an average velocity of 1088. Using 11.2 grains of 1680 under a 220 smk my SD was 38 with an average velocity of 1045. I tried many other charge weights in both these powders and the SDs ranged from 35-71.

Is there any thing I can do to get my velocities more consistent. My horizontal spread is good but even at 100 yards the vertical spread is 5-6 inches.

[320pf]

Originally Posted by silvery37

I am using an AR platform with a 16'' noveske barrel. My brass is .223 winchester cut and formed to .300 whisper. Using 9.4 grains of H110 under a 220 smk my SD was 55 with an average velocity of 1088. Using 11.2 grains of 1680 under a 220 smk my SD was 38 with an average velocity of 1045. I tried many other charge weights in both these powders and the SDs ranged from 35-71.

Is there any thing I can do to get my velocities more consistent. My horizontal spread is good but even at 100 yards the vertical spread is 5-6 inches.

silvery37-

I think the you may have a powder position problem. Try this experiment. Point the barrel straight down and then very slowly bring it to level and shoot the round over the chronograph. repeat this two or three times. Then point the barrel straight up and and then very slowly bring it to level and shoot the round over the chronograph. repeat this two or three times.

If you have a large difference in velocities between the two different test, then you are seeing the effects that different powder positions are causing in your loads. If this is the case you may want to try and seat the bullets deeper to minimize the volume that the powder has to move around... holding the powder in a more consistent manner against the primer.

I hope this helps... Good Luck


320pf

[silvery37]

Thanks I will give that a try. I noticed that if I dont count the first round in the string it drops the SD almost in half.

[Pitt300]

What does it do to your group size if you drop 1st shot?
Problem is-the 1st shot may be the only one that counts!