I recently moved an optic from my Remington 700 in 308 (made in 2012) to my Remington 700 in 30.06 (made in 1967).  Because the 30.06 is a longer action, I did have to move one of the rings on the optic, but left the other ring alone.  When I sighted the 30.06 in, I had to shift the optic 21.5 MOA to the left.  Is that normal?  What would cause it to be that far off?  Could the scope base screw holes be misaligned on one of the rifles?

Yes.

Yes, and more likely on the newer 308 rifle.

But the scope tube could be slightly bent, one barrel slightly off “blue print” specs, one barrel and action poorly bedded, one crown imperfect...

Or a combination of factors.

Not uncommon, but it sure is nice when you can pull an optic/mount, move it to another gun and it only shifts a few.

Did the 308 have a 20moa rail on it?

1.5moa of shift is expected at 100yd

But there isnt a difference in 21inches of drop between a 30-06 and 308 at 100yds

My bet is the 308 has a 20moa rail and the 30-06 doesn't

Update shift left to right is generally a problem with the base mounting

The vertical shift was minimal, about 1.5 MOA.  The horizontal shift was significantly more, I had to shift 21.5 MOA left to get it sighted.

I could see it.

I have had 3+moa windage in the exact same rifle with different loads.

Add in a curved barrel on one rifle a goofy receiver on another.......the offset could add up to that much, I suspect one of the rifles is especially bad though.

I wouldn't know if it's normal, it seems abnormal. Which rifle had the most even left right adjustment from zero?

I switched from a one piece to rings holding a US Optics ST-10 scope.  I didn't think to boresight it, and fired a couple of rounds through my chrono screens at a target at 100 yards.

No impact on the target but a side support for my sky screen was decimated.

I checked the 30.06 this morning, will check the 308 later.  From zero, the 30.06 has another 10.5 MOA adjustment to the left, and it has 32.75 MOA adjustment to the right.

If you were moving it from custom action to custom action, I’d be worried. From standard R700 to R700? I wouldn’t bat an eye.

I have several Remington 700s.  Remington does not drill the receiver mount holes exactly concentric with the bore.  They get hole spacing correct, but not concentric and not consistent from rifle to rifle.  I've always had to rezero when moving a scope between Rem 700 receivers.  If barrel length is different, velocity will be.  If different calibers or different loads in tbe same caliber, POI will differ.  Barrel harmonics will also differ.

In short, one scope can be used, but one rifle and load is my baseline zero, which I record.  Then, if the scope with rings intact is moved to another rifle, I count the clicks in elevation and windage to create the new zero and record that in my log book.  Then, the scope can be adjusted per the log book for an acceptable zero on either rifle. This only works if the scope is returned to the same rail slot or bases each time, and if the scope turrets track true, and the ammo for each rifle remains the same as used for the recorded zero.

You can do the same thing with a good collimator type bore sighter with the recorded zero change data.  This type bore sighter shows you a grid through your scope and you can precisely make adjustments in the location of your cross hairs on the grid, even if your scope turrets do not track particularly well.