So I'm trying out a new load, having gotten some bullets for free in a contest. I made three separate loads with them, used a chronometer, and I'm now confused as to the outcome. Here is what I came up with:
9mm, 147gr HP bullet, 1.115 OAL, Win 231 powder
3.5 gr. FPS
779
783.9
756.6
841.8
866.2
911.1
760.6
781.3
835.6
826.7
Average: 814.28
Spread: 154.5
3.7 gr. FPS
830.2
882.3
927.7
905.4
936.9
951.3
871.6
927.1
955.4
840.8
Average: 902.87
Spread: 125.2
3.9 gr. FPS
814.9
807.9
782.3
755.3
Error
816.6
779.5
906.6
855.3
848.7
Average: 818.57
Spread: 151.3
Notes:
3.5 gr. & 3.7 gr. both produced about fist-sized groups at 25 yards (free hand, seated). 3.9's group was just a little larger, but admittedly I didn't take my time as much as I did on the first groups.
My confusion lies in how similar the 3.5 and 3.9 groups are?? Why would they be similar (almost identical average). I would have thought the velocity would only increase with more grains. I was really careful in labelling them correctly. Is this a guarantee I messed up though?
Your collective wisdom is appreciated!
9mm, 147gr HP bullet, 1.115 OAL, Win 231 powder
3.5 gr. FPS
779
783.9
756.6
841.8
866.2
911.1
760.6
781.3
835.6
826.7
Average: 814.28
Spread: 154.5
3.7 gr. FPS
830.2
882.3
927.7
905.4
936.9
951.3
871.6
927.1
955.4
840.8
Average: 902.87
Spread: 125.2
3.9 gr. FPS
814.9
807.9
782.3
755.3
Error
816.6
779.5
906.6
855.3
848.7
Average: 818.57
Spread: 151.3
Notes:
3.5 gr. & 3.7 gr. both produced about fist-sized groups at 25 yards (free hand, seated). 3.9's group was just a little larger, but admittedly I didn't take my time as much as I did on the first groups.
My confusion lies in how similar the 3.5 and 3.9 groups are?? Why would they be similar (almost identical average). I would have thought the velocity would only increase with more grains. I was really careful in labelling them correctly. Is this a guarantee I messed up though?
Your collective wisdom is appreciated!
