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It would be interesting to try this:
If you hand load, neck size only (not full length for this test) and fire the same case 2-3 times, then measure using a headspace gauge. The brass will more closely resemble the chamber dimentions than once fired brass and then compare with the same measurement on your factory ammo. If you can still chamber the fired round, (if headspace is the issue) the problem factory ammo should measure longer.
Regardless, if the dealer will take them back, return them.
Good luck!
