I had an odd experience yesterday that reminded me of this thread. I had recently performed some testing with my Win 94 and M1 garand with a RD designed 310-178 grain bullet. I had covid a couple of weeks ago and felt like junk, so I just powder coated bullets and reloaded for almost 6 days straight.
For the M1, I sized the bullets to 0.309 before and after PC. They were water dropped out of the oven. The brass was freshly annealed and sized, then mouth expanded to 0.306.
For the win 94, I sized to 0.311 before and after PC, as the 94 has an oddly large groove size between 0.3095 and 0.310. The bullets were air cooled out of the oven and seated in brass freshly annealed and sized, then mouth expanded to 0.308.
Anyway, I loaded these bullets about a week and a half prior to the actual range trip. Then did my test earlier this week, Tuesday and pulled the unshot bullets last night. The bullets were extremely difficult to pull using my RCBS collet bullet pull setup. Like grumpy, sailor cursing hard. I was surprised how difficult these were to pull. I measure the pulled bullets and they were 0.001 to 0.0015 larger at the driving bands than when I loaded them. I cannot attest if the brass had any spring back at the mouth that could have added to the experience. The difficulty of pulling the bullets was nearly the same for
Caveat: This was my first time pulling Powder Coated bullets with a Tumble Lube design. Who knows maybe that is what made them harder to pull. I guess there is a scenario where my other bullets I have pulled in the past have rebounded the same way, but I had not noticed any issues pulling them from the case.
Anyway, these bullets did seem to rebound for some reason. I guess, I'll have to start keeping notes on this and see if I can find a trend.