:?
Subfan,
Reading your description indicates to me that you have opened the action and the spent case is stuck in the bolt, not the chamber. This has nothing to do with the need for a small base die. You may have tired brass, defective brass or reloads overcharged. Now, how to get it out? I would try using an angled Allen wrench inserted into the case mouth and an outwards pull towards the receiver opening with pliers on the other end of the wrench. If you get the case out, examine it for overt signs of excessive pressure. If there are other signs of excessive pressure, such as flattened and cratered primers or primer pockets with black smudges around their perimeter, I would suggest discarding the reloads. You may want to measure the case head with a micrometer if there are no signs of excessive pressure.