Ammo brand can certainly make a difference. But it seems to me that the problem you mention generally sorts itself out after a few hundred rounds are fired from these magazines. You could be having a problem that is a combination of both. I never get excited about this kind of problem until it hasn't gone away by around the 500 rounds downrange time. All new guns need firing a good bit for things to settle down and smooth themselves. My wife's copy had similar problems with the last round in the mags but it had disappeared after 300 or so rounds were fired. Go shoot it.

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So long ... Ken