While I haven't had an issue with it, I have noticed that the Nano mags don't run as well as the APX Carry mags do. The ever-so-slight changes* Beretta made to the mags make a difference. I hadn't though to ask, but were the issues with the APX Carry with the new mags, or the Nano mags?
* - Nano vs APX Teardown Thread - Magazines
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