Our military adopting the Grendel?

[JASmith]

...Does 6.5 Grendel Ball penetrate auto glass without being deflected?...

Only when the glass is presented normal to the bullet path.

Physics also tells us that every bullet regardless of caliber will be deflected to some extent when going through a barrier like glass when it is presented at an angle to the flight path.

There are apparent exceptions resulting from the details of the interaction, but the deflection always happens.