What brand sizing die and what brand / type seating die are you using? I have had good luck with Redding FL dies with the carbide expender ball and their competition seating die. What type of lube are you using on the case mouth when FL sizing? If the inside of the case mouth is not lubed...
Hard to know for sure, but a possibility may be that the expander mandrel could have had enough resistance to change the geometry of the shoulder of the brass, given the lists of facts that you listed.
Hondas with a solid rear axle will beat the shit out of you on fs / blm roads. Been there done that, now I use a Polaris Ranger and would not consider taking a 4-wheeler / quad out west now.
Also, a carbureted machine will suck at elevation. I still have my honda 500 and it is great for what...
Technique specific:
I have found too much face pressure on the stock will torque the rifle during recoil and can cause horizontal poi shift.
Not maintaining control of the rifle with your firing hand can lead to horizontal poi shift
'slapping' the trigger
Too much 'grip pressure' with your...
This makes me think your scope is not adjusting internally, even though you are dialing. In your OP, you mentioned checking your apps out to 650 yards and checking return to zero. Did this this involved shooting at 650 yard targets, or just comparing the apps firing solutions?
I’m not familiar with Swaro scopes. Are you sure each ‘click’ is 1/4 moa and not 1/8 moa? Also, have you chrono’d this rifle / ammo? Try shooting at 200 yards without dialing and don’t hold over. Just hold same as 100 and see how low your poi is
You could build a single shot on a T/C Encore receiver, if you can find one at a reasonable price. Most likely you will have to overpay for one since they no longer make them. I built one with an MGM barrel. With only a handful of rounds through it, I have shot 5 rounds into approximately 1"...