@wildwildernessIm sure you have heard that old "chrony"s can be off on velocities (from personal experience as well) .... would be interesting what a LabRadar says, or at least a Magneto Speed.
That said, I had a 35 Whelen that has been re-barreled to a 9,3x62 with better results. Had fail to fire issues with the standard whelen. maybe the AI version would be better.
Lab radar, magneto speed or chrony chronograph are all much of a muchness. I have checked my chrony with a magneto speed and there was only a few fps in it.
When I set my chrony up I always do a baseline check with 22lr target ammo. This ammo is very consistent and gives 1070 +- 10fps, the same as on the box. So I can assume that it is reading correctly.
Your fail to fir with you whelen sound like a headspace issue either from the start or from bumping the shoulder to far back when reloading.
Mine is a push feed action and even empty primed cases go bang. Even the 400 Whelen notorious for minimal shoulder if set up correctly has NO failure to fire issues.
I'm glad you like the metric Whelen .