Dimensions off on final part
Yup that is what happens. It is simply the plastic cooling and shrinking. It will happen on just about any printer. 0.3mm on a what 40mm part. That is 99.3% on target. 

There are some great blog links about it, 
and here is a Stack overflow where I talk about it more in detail.

The only mitigations I can think of is
1) use a hear chamber.
2) use a SLA 3d printer.

I wouldn't worry about it. Just make sure your designs have good tolerances.