Re: 300 WIn Mag confusion
I guess I'll wade in on this as I've had it happen a couple times, exact same deal. What I found is it's not from being a tight chamber but long head spacing, what happens is you fire SAMMI spec brass, which is a couple or few thousands smaller than a min spec SAMMI chamber, in a chamber that has been head spaced over spec. In the times I ran into it the chambers were over spec by .009 with put me at .013 head spacing, when you fire the firing pin pushes the case forward the when it fires the case slam back which can give you flatter than flat primers and can lock you up or give you some heavy bolt lift, usually factory will shoot better due to them being loaded lower than hand loads.
A quick check for this is to just put some scotch tape on the back of a none fired case, layer on the tape till you can't drop the bolt, each piece of tape is around .002, if you get out past .010 your going to need some tools!
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