How on earth can hot loads cause sticky extraction of UNFIRED rounds? Read it again, boys, fired cases are extracting just fine.
Your loaded cartridges are somehow misformed, and the AR is ramming them into the chamber. The pressure of firing them is forming them to the chamber, so they behave normally after firing, but unfired rounds are jammed in there too tightly to be pulled out easily.
Some possibilities:
- The cartridge is too long and the bullet is sticking in the rifling. If you are feeding from the magazines, this shouldn't be the issue.
- You are applying a heavy roll crimp, this is causing the shoulder to buckle, and creates a bulge at the body-shoulder junction. I have done this on loads for my .250 Savage.
- Your case is not being sufficiently sized at the head.
My suggestion is that you take a problem round or (better and safer) a dummy loaded the same way, and use a black marker to colour the tip of the bullet, the shoulder and neck area, and the case web area. Let the ink dry and chamber the cartridge, making sure the bolt goes all the way forward. Now, remove the cartridge and see where the ink is rubbed off. That is your trouble point.