Some possible reasons:

-You're jamming the bullet into the lands. Book data goes out the window when you do this.

- Your scale is off. Test with check weights.

- You thought you grabbed 4064 off the shelf, but it was some other number salad like 4895.


XC is right... all of those pieces of brass are telling you No Mas. Also, when you're adding powder but the speeds aren't increasing it's time to stop.