I am stumped... I have a 700 in 375 ultra, I worked up a load with 270 tsx and 98 gr. of H4350 (3150 fps) It ended up being a little too hot and was stretching primer pockets after about 2-3 reloads so I backed it down a half grain, then another and so on I am not down to 96.5 grains 3030fps and the more I shoot it at 96.5 grains the harder and harder ir has been to open the bolt. I was only neck sizing but decided to FL size once and it didnt really do anything different. Still has bolt click and a couple times I have had to beat the bolt back. It does fine with an empty chamber. I bore scoped the chamber/throat to make sure there was no carbon ring or anything that looks like it may be causeing an obstruction to increase pressure. There is some copper in the bore and there is a chance I have not been getting it all out. I use wipe out and gave it the boretech test and it passed. Next time i think its clean ill borescope it to be sure. I know I can just keep backing off the powder till pressure is ok. but with it getting worse and worse each time I fire 96.5 i think there is more to it. I am about 50 fps over book max with a 2" longer barrel. Also im on the 5th firing and my primer pockets are still nice and tight. I am hoping its a copper build up and I just need to be more thourough with my cleaning but...im a little skeptical...throw me some ideas guys.