Not all competition is from a bench or bipods. Isn't NRA highpower a 3 position match?
Yes and zeros will be different. My 200 yard standing zero is different then my 200 yard setting zero. My rapid fire zero is different then my slow fire zero.
Shooting from a bipod or bench is going to give you a different zero then shooting prone with a sling, or setting, or kneeling, etc etc.
You may have a perfectly plum scope (zero can't) but as you move out spin dirft does come into play. Most people discount it, but its there, granted its normaly hiden in wind est. errors, but its there. How much depends a lot on the twist rate.
Look at your ballistic program. Take SHOOTER for your Ipod or I phone. Plug in all the numbers, set wind at ZERO and wind direction at 0 or 180 degrees. Now check the windage correction to, lets say 1000 yards. Shooter will give you a correction in this no wind situation.
Now go back to your inputs on your SHOOTER program, don't change anything but the twist direction. Change from a right hand twist to a left hand twist (leave everything else alone). Check your wind drift numbers, they are reversed.
Check the clicks on your windage knob, are they a constant 1/4 min all the way out to 20 min left and right??? Same with elevation clicks.
DATA BOOKS, write everything down.