Point of impact changes

[Stein]

I had my scope get adjusted a full turn last year somehow.  I completely missed a deer low at 104 yards.  I couldn't believe it until I took no less than 3 practice shots.  I still have no idea how it happened.

[jasnt]

my bet is a loose base screw

  this has happened to me on my 300wm and just happened to a friends 270

[CaNINE]

temperature difference and a really sensitive powder?  Maybe the swing in  chamber pressure is causing the bullet to leave the muzzle at a different point in its vibration or recoil?

Pressure changes with altitude, but temperature and humidity also change it so an increase in altitude of 3000 physical feet might be effectively a lot more if you sight in at sea level on a really cold day with no humidity and then climbed 3000 feet higher and shot on a really hot, humid day.  I can't imagine any change in weather that would cause that much of a shift though.

It happens.  I've had well over 6 MOA in variation with Reloader 33 in my RUM.  If you zero at 80 degrees at sea level then hunt at 3000 feet at say 40 degrees you may see a significant shift depending on the powder used.  This is why temp stable powders like H1000 and Ramshot Magnum are so popular.  I freeze my ammo overnight and then test to see if my zero will shift.  If it does the load is no good.
   
 

What powder are you using?  If you're not using a temp stable powder you could see that much shift.  What were the environmental conditions when you zeroed verses where you are shooting now?

Not a chance. If this is true,rifles would make better clubs.

[Curly]

Bean, did you end up getting a new scope for your .270?  If yes, what did you go with? 

[Curly]

You will probably want to double check all your scope mount screws before next year.

[Bean Counter]

Bean, did you end up getting a new scope for your .270?  If yes, what did you go with? 

Yep, sure did. Got a Zeiss HD5 3-15x 44mm. Has Rapid z800 recticle. Some might find it cluttered comPared to a basic duplex reticle i find it ingenious. Had to forego a buck deer tag in Wyoming this year to make it work with the budget but it was worth it. Smoked a few doe/fawns at 200-400 yards once I got it dialed in.

Enter the particulars of your load on their calculator at Zeiss.com. If I keep mine set at 12x I can align the BDC lines and they're within 10 yards for the bullet I shoot. It's so easy a bean counter can do it.