It sounds like the die is too aggressive for your chamber,measure the fired brass at the 200 line, then measure a sized piece.i think you will have your answer.I have one for the 6.5 Creedmoor and truthfully I am really struggling with the die. Not much I can do about it as support is non existent unless you sign up for the $15 forum they have. My issue is it is really difficult to run my brass in it. I use die wax, I have tried the Hornady One shot, etc and still really effort requiring to get the brass back out. I have not stuck a shell in in yet... Would like to know if it's just me or what.
I did see on his YouTube channel that he finds he needs to run it through the mandrel die without the mandrel as it also sized the case to the base, then puts it into the full sizing die. I took my cases to neighbor and was able to easily run them thru his RSBS 6.5 creedmoor sizing die.