Home Forums Reloading Big Game Rifles 300 WSM headspace growth

If you look at a SAAMI chamber and cartridge drawing it lists chamber headspace as min and max and this covers .010. And then between the GO and NO-GO gauge you have .004.

I collected milsurp rifles and the worst variation was on my Enfield rifles with .017. And the worst on a new rifle was new cases being .011 shorter than the chamber. Meaning the case was .009 shorter than the GO gauge and my chamber was in the middle of the GO and NO-GO gauge.

Bottom line and my guesses would be hopefully some how your measurements are way off. Or the worst news is your have sever lug setback and you need to have a gunsmith check the rifles headspace.

I do not know how old your rifle is or how long you have ben reloading for it and I hope its human error in measuring. BUT the short magnum cases had a bolt thrust problem. And this was made worst if any oil or grease was left in the chamber. And the headspace would grow very quickly if the chamber was not kept dry.