I'd like to be a fly on the wall at that range. You'd get some strange looks and some people getting behind you - far behind.
The hottest I ever went is one half a grain over and that was with the recommended primer. 3 grains is a lot, and with the magnum primer, you might as well call it 5 or more over.
I've only seen signs of excessive pressure once in one of my rifles. It was a Marlin 1895SS in .45/70 and I was using loads from an old manual. I believe that some of the hotter loads were meant for the Ruger 1 but the manual stated that strong, modern rifles would handle these loads. I got a stuck case with the maximum load and that was the last time I used that load. Better to be safe than sorry. When using maximum or above loads, you should always work your way up in small increments and back down at the first sign of excessive pressure.