I went to the range last Wednesday to do my final preparation for our annual State Championship Military Bolt Action Rifle Match. In previous trips to the range I had narrowed the selection of loads for the 30-180-SP bullet to powder charges of 4227 from 15 gr. to 18 gr.
Before I go any further, I should tell you how I record my groups.
20 ( 2 1/2 H X 3 V ) 20- G- 3 indicates that I shot a 20 round group that measured 2 1/2 inch horizontal by 3 inch vertical and it measured 3 inch diagonal.
In addition, 20 [ 18 ( 2 1/2 H X 2 7/8 V ) 20 ( 2 1/2 H X 4 1/2 V ) ]
18-G-3 indicates that I shot a 20 round group of wihich 18 rounds measured 2 1/2 inch horizontal by 2 7/8 inch vertical AND the 20 rounds measured 2 1/2 inch horizontal by 4 1/2 inch vertical and, 18 rounds measured 3 inches diagonal.
I like to shoot a 20 shot group because in basic statistics the greater your sample size the more realiable your prediction of results.
The following are the results of my tests at the range:
15 gr. 4227 20 ( 3 3/8 H X 2 3/8 V ) 20-G-3 1/4
16 gr. 4227 20 ( 2 1/2 H X 3 V ) 20-G-3
17 gr. 4227 20 [ 18 ( 2 H X 1 7/8 V ) 20 ( 2 1/2 H X 2 7/8 V ) ]
18-G-2 1/8
18 gr. 4227 20 ( 3 1/8 H X 2 1/2 V ) 20-G-3 1/4
Based upon the above data I have selected the 17 gr. load for the
30-180-SP bullet to shoot in the match.
Sailman