0 MOA or 20 MOA base?

[jasent]

the 6.5 creed is going to drop out of the air and tumble at a little past 1300 yards on a 24 in barrel. With a 300 yrd zero your MOA adjustment is under 50 MOA. With that said I do think Talley makes excellant products.

This is just bad info. Bullets don't just fall out of the air and tumble unless they are under spun to begin with. 95% of bullets on the market today will transition to subsonic if spun correctly from the start!

 

[NZScotty]

20 MOA. I talked to a Leupold tech and he enlightened me about something I never thought about. As you adjust the turrets for elevation, the crosshairs are move into ever decreasing space in the scope tube. With the MOA mount, you will stay further away from the decreasing available windage adjustment. I don't understand why it does it, but he explained that if you do a ladder test, it could cause a horizontal error. as you move the crosshairs into the ever decreasing part of the scope. Like I said, I don't fully understand why it induces a horizontal error, but he is the expert.

That's an interesting point about keeping everything centred as possible. We've applied it plenty to windage issues(especially with swaro scopes on some of the brownings we get in NZ) but never really to elevation unless a scope was near to maxing out for a given setups application.
If this helps any with getting your head round the horizontal error. If windage isn't near centre as you adjust up it is possible for the erector system to basically be pushed over by the radius of the tube, giving horizontal shift. Same as how a poorly aligned scope can rob you of up adjusted due to being wound right out to one side to get centre.