it could be but you can confirm whether or not by measuring before and after, it has to be a fired in your chamber case to find out
just having a 5 thou increase in diameter from saami spec would not make the case harder to chamber
here is a saami spec diagram to show what the measurements should be (roughly) depends on the reamer used
the bulging happens from one time sizing, it doesn't happen over time because your case forms to the chamber each firing
so you have a fresh start every time you shoot the case but it may take 5 shots from neck sizing to get your cases to perfectly form to your chamber
if your die is screwed down to much it can crush below the neck so you get a bulge or mushrooming effect
that's what you should be checking for and the answer is don't screw the die down so far, if this is the problem
I hope you are understanding what I am talking about and in regard of the die it doesn't matter who makes it this can happen with any brand
let me know if the cases are bulged?
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