I have a Redding 375 H&H full length sizing die that I have not used before. I picked up some once fired Remington brass and am having problems trying to resize. Before I used the die I removed the decapping assembly and made sure the die was clean inside and that the expander ball was clean. The brass is clean and I use Imperial Sizing wax for lube. I tried several different cases and on each when the neck came in contact with the neck of the die it basically stopped. I put some pressure on and it only went in about a 16th inch. It took a fair amount of force to remove the case. If I were to go in farther I think the rim would rip out of the shell holder and the case would become stuck when I tried to remove the case from the die. Same result with the decapping rod and expander ball removed. I did have a couple pieces of brass that had already been resized (not by me) and they will go all the way in the die to full contact with the shell holder, so the die should be within tolerances. The once fired cases mic around .405" neck OD and the resized ones mic around .390". Even when I am necking down brass to a different caliber I don't encounter this much resistance. Only thing I can think of is that the brass is extremely hard. It isn't nickel and I don't think it is more than once fired. I have never annealed before but I guess I could try that. Any suggestions or feedback?