POI Change Mystery

[bowbender6]

Last month while hunting I thought I should be able to adjust my scope to match my shooting conditions. I have my Savage zeroed at 170 yards with 300 BO, BCR and 60 gr of N120 going around 2275. This is good for the CRP fields I hunt. Behind my house 100 yards would be a long shot so I adjusted my scope. Normally I am 2.5” high @ 90 yards so I adjusted my Sightron Big Sky II 4-16x with target knobs down 2.5”. The next day I thought I should check just to make sure it POI moved the right amount. He shot hit the edge of a ¾” dot @ 90 yards. I thought this was good. I can shoot at my house so I usually don’t leave it loaded between weekends. After a couple of weeks and some shots I rechecked zero and POI had changed to 1.5 “ low @ 90 and about 2.5” low @ 170 yards. I just compensated with the scope adjustments and shot three more does. Last one was 112 yards in the neck. After season I am trying to figure what happened. Groups are under 1”MOA @90 yards. Ventliner is .032 (gauged) and hasn’t changed. Barrel wasn’t cleaned. Stock is bedded but nothing was removed or losened. Velocity is the same.I am puzzled. Think something happened in the scope?
Here is my last target. Shoudl have been zeroed

[edge]

Is there a temperature difference from now vs a month ago?

Jeff had a problem with ignition with N120 while tar12 did not.
You might want to chronograph to verify that your velocity has not changed.

edge.

[wilmsmeyer]

I would also square test your scope and rule out a problem there.

[Chris Champion]

Tim,

I have had some odd POI changes with my set up recently too. This weekend I plan on pulling everything apart and will put the scope on a 30-06 that is a known accurate gun, (again), and do what Wilms suggested to verify that I'm not having an issue with my Conquest. However, my gun is not bedded so I may have something going on there as well. I'm interested to see what you find out with yours.

[bowbender6]

The temp is about the same (25 degrees). I started recording the temp in my shooting log. The velocity is about the same. The gun is clean now so I need to fowl it and do the square test for the scope. I think I wil use Rem 300 gr they seem to shoot abot as good a the BO and are a lot cheaper.

[wilmsmeyer]

Ya know I sometimes have to take a step back and think about everything. It seems that all my guns have shown POI changes at different times of the year. We have dramatic temp differences where I live. I can shoot at below 0 or almost 100 degrees. Slug guns, my .243 and .17 and my Savage have all posted groups not where they should be at different temps. Why? I don't know. Physics of some sort I'm sure.

What I do know is that I always take shots with my hunting guns thru-out a hunting season. Whether it's summer or winter, I always shoot a gun often if I am in hunting mode. There is usually minor tweaking involved, not much, but some. I've come to accept that I just need to constantly confirm and that my set ups are fine. The exterior elements do play a minor part in POI as they change.

I still suggest the square test. Reliable scope adjustments are, to me, more important then the best, clearest glass. A square test will reveal lots of things.

[bowbender6]

I tend to agree Wilms- I am a little anal about checking and rechecking - I think it has something to do with Murphy.