change of poi as gun warms up?

[svandamme]

I'm relatively new at this, have about 350 rounds down with my PM7.
It shoots low, have adjusted the sights up.. But i get the idea that the point of impact changes as the gun warms up?
At 10 meters, If i aim for dead center when cold , i'm below the black.
But after 30-35 rounds, i'm right on the money where i aim.

Had this several times now.. but not sure if i am doing this myself, or does the POI considerably change as the gun warms up?