I'm familiar with the causes of vertical stringing in general but I'm unsure when it comes to BP load development and fouling control. I was wondering if the experienced BP folks know specific things with these factors that can cause vertical stringing. I was shooting my TD with 68gr of Swiss 1.5 with a .060 wad using 512gr 20-1 cast boolit. It not only shot way higher than the sight setting (I had to to set to around 175yds for 200yd target) but the shots were are center but extreme vertical spread of 12+ inches. I believe the wad adds to the higher POI. I was just using a blowtube of 1 long breath between shots.
Last thing, the bullets are only .459 and much smaller than my groove dia but it seems they were properly obturating since they were center and stable. I would think if them being undersized was the major problem it would not be vertical stringing but more of a trainwreck pattern. Any ideas? Thanks.