Which bit
Bullet speed seems a tad ambitious.
Blimey.
As the bear suggests, if your empties are giving you a stiff bolt lift, on something as small as a Hornet, well, its a classic sign of over pressure (quite bad overpressure as it goes, usual early signs are flattened or cratered primers and the case being burnished by the opening bolt rubbing on the case head).
Your cases are not able to spring back and eject which means the poor little things are not well.
I'm a maggot in another life you know
the Hmr head doesent weight 18 grains quite a bit more
I'd hazard a guess that the chrono is reading bit's of wadding blown out ahead of the ball
I can manage 3450fps with a nice aerodynamic 30gn from my "K" but that's a compressed load 13.7gn of lil-gun, & under 750fpe