Thank you everyone for contributing.
Paddle - where I hunt I have visibility out to 200 yards. That said, the farthest shot I've ever taken from that stand (over 20 years) is 150.
Personally, I've used the same gun (Rem 270 7600), same ammo (Rem Core Lokt 130gr), the entire time.
I was just curious to see what everyone thought about my son's new gun being 3" low at 25, whether it could have been deliberately sighted in that way (it WAS dead on left/right), or if the scope was way off.
After reading more ballistics charts and playing with the numbers, I have a strong feeling that the scope was off - there was no combination of numbers I could plug in to make it reach zero when it starts off 3" low. This has me a bit worried about the scope, if it can be knocked that far off - hope it's not defective (my brother-in-law bought a gun - we sighted in the way I always do, it was grouping very nicely. He got in the stand and missed 4 shots under 50 yards - never banged it, dropped it, nothing - re-sighted in opening morning !@&$%^#, and he missed another one - found out the crosshairs were loose inside and moved when he slung it).
My other feeling was that the seller just stuck a scope on the gun to make it more attractive to a buyer - he couldn't tell me the last time it was ever shot. Hope this is the case.