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I've recently been testing out some new .308 loads using Wildboar and today had something weird happen...

I normally shoot at 25yds (my club only has 25 and 50 yds ranges) and last Sunday I tested some batches with different charges, and also chrono'd them to try to get into the 2600 to 2700 fps range with 155 SMK's... only 18 inch barrel... and 44.0, 44.5 and 45.0 grains were in that range. (We have a club outing to Bisley and 900yds at the end of the month, so trying to get something suitable to reach that range.)

I normally shoot 178 gn Amax's and the rifle was zero'd at 25yds for those. The 155gn SMKs were hitting just under an inch high of my POA, but I didn't bother adjusting, just going for group size.

Today I tried more batches going up 0.2 grain at a time, 44.2, 44.4 etc up to 45.0, but I moved onto the 50 yd range to check group size better..

With the longer range, I was expecting the shots to go 1-2 inches high, so imagine my surprise when the first shot went 6 inches LOW...!
I dialed in 10MOA on the scope, and that then put them about 1/2 - 1 inch high of my POA.... and all the shots fired stayed around that as I went through the batches.

I was shooting from a bipod last week, but switched to a bag this week so that may make a little difference, but not that much!

i've checked the scope base and rings, all tight and the action seems tight... I'm puzzled...

So... what would cause a rifle / scope to shoot 10 MOA low between 25 and 50 yds..?

Your round will still be rising at 25 yards and even 50yrds to cross line of sight I would think

Don't forget your scope will be about 2" above the barrel bore

Yes, that why i expected the 50 yd shots to be an inch or 2 higher than POA, as its still rising.

I think the above goes against all the laws of balistics, so there must be some other reason...

The only possible thing I can think of is that I turned the turret a whole turn the wrong way.... Thinking about it, last week i did dial the turrets down 5MOA so I could put 2 groups on the same target... I think when I went to turn them back to zero, I must have gone the wrong way so my sights were 15 MOA low to start with today..(my turrets are 15MOA per revolution)...

That then makes sense...

The turrets are currently still at 10MOA, i'll turn them another 5, so on the 0 mark, then try them again at 25yds next week... I have a feeling it will be pretty much shooting to POA... If it isn't, I'll be very mystified...!!

You have two zeros at each distance because of the looping trajectory of your bullet. My head explodes if I try and understand it any more than that though....

Your change of shooting rest can make an impact on the POI/POA variances.
If you find your turret issue isn't the problem then try shooting from the same rest at both distances and see if that has an effect.