Checked the zero on the .270 yesterday in preparation of some stalking. It was wet and windy and I couldn't be bothered to walk to my usual spot but there was a huge logpile with a hill behind it that made a perfect backstop so I used that. I use a 200 yard zero and I could only just get 200 yards at this site. I pinned the target onto a 4 foot diameter stump that was at the front of the pile and trotted off to the 200 yard mark.
Prone in the wet mud I discovered that owing to a slight rise in the ground about 120 yards to the target, I could only see the centre bull and maybe half an inch of white card below it. Never mind, 120 yards in the bullet is going to be at least an inch high so no problem as it ought to be at least 2 inches above the grass at the closest. Ten shots and wandered back to the target. The group was at least 4 inches high and 4 inches right of the centre. It was also over 3 moa. Moved in and left to 175 yards where I had a clear view and the result was the lower group.
So what happened? I know people will say the bullets were touching the ground but I'm sure they weren't as I would have seen the spray off the wet grass and anyway there must have been a couple of inches clearence at least.
I wondered if the shockwave from the bullet is sufficient to move it if it's in close proximity to the ground or is this complete nonsense?
The red circle is where the first group of ten went, the second group was from the 175 yard mark and a 3/4 inch group which is what I would expect.
Mel