Update on the sizing dilemma. Long story short, it was a lubing issue as many here had mentioned.
Ordered another Redding FL die from Midway and received it a couple of days ago. Went to the range and fired a couple pieces of new brass, cleaned them and did not anneal them.
After cleaning out the manufacturer oils I applied a little bit of imperial sizing wax to the inside of the die and expander ball. Was immediately met with a lot of resistance same as the last time I stuck the case, but kept relubricating and working it just a little bit further each time. Eventually, I got the first piece to size all the way. After that the die worked fine on the non-annealed and annealed brass. The press still had a decent amount of resistance but was MUCH smoother, night and day difference.
Just needed to break in the new die and get it properly lubed. Was definitely afraid of applying to much wax and denting the case, I’ll keep an eye out for that though from now on.
Sent an email to Redding concerning my issue and their response was:
The 6.5 PRC has been a problem child with case sizing here is the method we have found to work the best.
First use Imperial Sizing Die Wax pre treat inside bottom of die with imperial on a swab, lube case with Imperial and size only 1/3 of the case remove and lube again install farther in die then remove and lube again this time inserting all the way into die. Generally after 2 to 3 cases using this method sizing becomes much easier with much better results.
This cartridge has been troublesome since its introduction for sizing we have found that this method using Imperial is the best way to go.
A lot of overthinking the situation here but I learned a lot. Hope this helps as it sounds like some other new 6.5 PRC reloaded might be running into these issues!