If the velocities are way off, the shots might spread out vertically at longer range since the slower bullets have more time to drop. There are also some weird things that happen if the bullet goes from super- to sub-sonic between 10 and 25 yards. If the bullets are tumbling once they leave the barrel, then the effect gets worse the longer the bullet is flying too. I guess these are pretty odd situations, though, and probably don't matter unless you've got a real tack driver in a solid benchrest. Maybe the rule would be that really crappy loads are even crappier at range?
The shooter's skill won't matter, once the bullet leaves the gun it does it's own thing if it goes 10 yards or 1000. You're just as good or as bad a shot no matter how far away the target is, although your brain starts messing with you when the target is way down range.
One thing to keep in mind is that at 10 yards you might not notice accuracy problems that you can see more easily at 25.
-J.