You checked the chamber with a head space gage, something like go-gage length +.001”. I am the fan of transfers, standards and verifying, I believe in verifying.
After adjusting the slack adjuster with the go-gage transfer the the go-gage to the press/shell holder, raise the ram then (with the primer punch/neck sizer plug assemble removed) and adjust the go-gage down until it contacts the go-gage shoulder then stop and secure the die to the press with the lock ring without turning the die, the die must be held while the lock ring is secured. After securing the die in the press and adjusted with the go-gage the die is adjusted to size the case to a go-gage length chamber, a skilled reloader with a feeler gage can determine the difference in length between the go-gage chamber and a minimum length /full length case by measuring the gap between the bottom of the die and top of the shell holder. Others? Just talk about it.
Get to know the tools you use, become familiar with the tools you use. Me? I reach for the feeler gage, the companion tool to the press. The length of the chamber, the ability of the press, die and shell holder to restore a case to minimum length/full length size a case can be correlated with ‘THE GAP’ between the bottom of the die and top of the shell holder.
Shell holder and head space gage? When a head space gage is used to determine the accuracy of the die there is almost always a problem with the head space gage fitting the shell holder, do not panic, remember I said the deck height of the shell holder is .125”, therefore it does not matter what shell holder is used as long as the deck height is .125”. After that there are shell holder looking shell holders that are bullet swages, can not miss.