I didn't watch the MAC video again, but I think that's the one where, when the gun didn't fire, he pushes the trigger forward to try to make it fire again.
You can't do that with nearly all striker-fired guns -- as the slide must be moved at least a small distance to reset the striker. Actually, he should have racked the slide and got a fresh round! He did all of this after dipping the gun in mud, and then rinsing it off in muddy water. Rinsing it off didn't reset the striker! He never did that...
It just shows that the guy doing the test doesn't know much about the gun he's testing, or what is an appropriate response for a failure-to-fire in a striker-fired gun. (He has done the same thing with other striker-fired guns, too.) I'd look at other tests and reviews before being too concerned about the MAC test. The folks on the FN Forum who have purchased the guns like them.
FNH, recognizing the lack of after-market parts, is working with a number of after-market vendors to support the FN-509 and FNS line, and Apex is working on a trigger upgrade kits for both, too. (I've got one of their kits for a Glock. It was expensive but very nice!) I have two FNS-40s (one a 40L, and my only complaints -- which isn't a big one -- is the trigger). The FN-509 is arguably a better weapon than the FNS guns.
The FN-509 and FNS share many design features, and the upgrade parts for one may work for the other. Unless you can find an FNS at a greatly discounted price, I'd go for the FN-509. (There have been some discounts on the FNS guns, however.)
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