This is somewhat normal. I have a P944 that will do the same thing every once in a while if I use to much force to seat the magazine. It has happened on other guns I own also.

Does it do it every time you insert a mag or sporadically?

It does it 99% time. I have 5 mags for it, 3 of them are factory, two are not and they all do this. I just sent my Sig P250 .45 back for this same problem. It started after about 100 rounds. I clean my guns after every use so I don't think it's from that. Come to think of it, my PT100AFS has done it 2-3 times out of 500 rounds but very rare. I have heard some people think that it's an added feature, but if the gun was not made to do it it's not cool to me. Also, I am not SLAMMING the magizine in, just slapping it enough to hear the click.

3 separate guns, different brands, that all do this? What are the odds?

Man, I swear I'm not too rough. Especially on the Sig. It's my baby.

My U22 NEOS dosen't do it!!!!!!!!