went to range today for testing… here's some info
180gr Speer Grand Slam, Trail Boss Powder, Winchester LR Mag Primers, .015 Jump, Lapua brass
First i loaded some single shots to be safe and slow down carefully(then 3 rounds of the lower weights each)
13 1277fps
12.5 1235
12.0 1202
11.7 1164
11.4 1172
11.1 1114 this shot a nice tight group, but i kept driving down the charges
11.1 1131
11.1 1117
10.8 1065 this opened up a bit, also possibly the beginning of key holes*see pic*
10.8 1092
10.8 1082
10.5 1068 still around same size as 10.8 group but also maybe keys
10.5 1059
10.5 1059
10.2 1044 a tiny bit tighter and i think keys, stopped here
10.2 1032
10.2 1027
When i looked at the target, the "black" around the bullet holes wasn't round after a point *see pics) so I assume this is key holes… I'm going to try out some Sierra 180GR round nose this week also… Also afterward I shot some of my regular loads to be sure I wasn't just shooting poorly… I wasn't
, this subsonic thing is a nice puzzle