From what I've read and experienced myself you need to foul (lead) the barrel a bit. I've put 40 rounds through mine and saw a significant improvement in grouping. I experienced the same vertical stringing when I started, but wound up with a very nice group with my last few rounds.
Apparently I can't attach pictures and the link didn't work either.
JG
Apparently I can't attach pictures and the link didn't work either.
JG