stringing can be caused by a bunch of factors, in my experience, wind and /or shooter form are the main causes.
Case in point, here is a 500 meter target with horizontal stringing that has nothing to do with the load or anything else but shooter form and /or wind calls.
It was shot prone with an iron sighted match rifle .
The Vbull is 1 MOA or about 5 inches, the 5 ring is 2 MOA or about 10 inches
Cat
[Linked Image from i.imgur.com]


scopes are cool, but slings 'n' irons RULE!