If Remington says it is OK, when you get it back, as long as you resize the brass and only bump the shoulder back .002", you should no longer have a headspace issue. When you have too much headspace, the brass grows like a balloon quickly, and slams against the chamber, and can cause signs of pressure. Swelling inside the chamber, slamming back into the bolt face creating ejector marks or flattened primers, etc. To me, your brass did not show much signs of overpressure. Just the sticky bolt lift and failure to eject could easily be a burr and bad extractor. But.....good to be on the safe side if you are not sure. Keep us informed on what happens.
If you do get it back with a clean bill of health...
1. Load the fire forming brass lighter, and shoot them to form in your chamber.
2. Buy a headspace gauge
3. Set your dies up to YOUR case length bumping shoulder back only .002". Not all chambers are the same. I have found .005" variance in R700s in 7RM alone. Add Ruger, Savage, and Winchester in there, you could easily have a bit more variance in chamber dimensions.
4. Reload and start your load development just like any other cartridge. Similar to any other fire forming technique. Like an Ackley or other "improved" version.
5. Find your load, and shoot it.
6. Kill a lot of animals with it.
7. Eat those animals.
8. Repeat
9. Eventually, rebarrel it when you burn it out.
