When Lil Gun first came out, they had no data for the K-Hornet - so I called them.
The tech I spoke to, told me there was no way to get enough of that powder into either a Hornet, or K-Hornet case - and exceed max pressure.
But, Lil Gun did not compress well.
In those rounds, Lil Gun gets more velocity with less pressure, due to a "lower and longer peak on the pressure curve".
When I later saw charts of the pressure curve, it became very clear what I was told was true.
I'd look for another cause of your problem.
Please keep us informed.
