Vertical in a group usually means that you need to add more powder or use a hotter primer.
A stiff wind blowing in your face can cause this type of stringing.
Resting the forearm too far out on the bags can cause verticle stringing.
Allowing the 270 to free recoil can give vertical stringing.
Barrel touching in a small place can cause a problem.
And for goodness sakes, try getting rid of the bedding underneath the barrel. It can help in certain circumstances, but in your case, I would suspect it.
Another thing, if your magazine box is binding inbetween the floor plate the the action, it can cause all kinds of bad things to happen. You should be able to drop the floor plate and feel the floor plate wiggle up and down real easy...this destroys a lot of guns accuracy and rarely do you ever have anyone mention this little tid bit.
Good luck!
