Originally Posted by BillPa
Without those things on hand the easiest way to check, sacrifice a piece of brass. Using one of the rough chambering pieces, first cut the neck off a just barely into the shoulder then chamber it. If it still chambers hard the neck and junction portion isn't the problem.
If its still rough, cut the same piece of brass off just behind the shoulder then try it. If it still chambers hard its a body issue, then you need a small base or a custom die to size the body more without additional shoulder bump.