Yes - as xausa says - form some brass, then check the neck wall thickness. I would formed a case and attmpt to chamber it. If it goes in easily, I'd load a bullet in the case and try to chamber it. Now, if resistance is felt on empty ctg., it will be from the neck area. Smoking or marking the neck with a felt pen should show if the necks are too thick or scraping while chambering.

I would not be too quick to ream or turn the necks - if not necessary. You really only want about .002" to .003" clearance between a loaded ctg. neck and the chamber neck walls. Some rifles, especially today, can have chamber necks up to .008" larger than the loaded ctg. neck.

Another method of checking. If the round chambers, then loading a moderate load and firing it then attempt to shove a new bullet into the fired case mouth will show if the necks were too thick - ie: if a bullet will not enter a fired case, then the necks need reaming or turning. Outside turning is the preferred method as it is more accurate - ie: you turn the necks concentrically around a mandrel - first removing the 'high sides' which is sometimes 'more' than enough.

Inside neck reaming will not make the neck walls concentric, as it merely removes metal from all the way around the inside neck. If the case necks are not of even thickness all the way around and they aren't, this neck thickness error will remain after they are inside reamed. Being .002" to .005" out of round is common.