FN FNS-9 report and tech questions


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Shmackey
February 3, 2013, 12:33 PM
Just took my new FNS-9 (http://www.fnhusa.com/l/products/law-enforcement/handguns/fns-series/) to the range yesterday. For those unfamiliar with the FNS series, they're very similar to full-size M&P pistols--basically Glocks with thumb safeties and good ergonomics. Plastic striker-fired 1911s, if you will. The FNS pistols are even more lefty-friendly: everything except the takedown lever is ambi.

My FNS-9 ran perfectly straight out of the box with medium-oomph reloads and hotter. It did not like my powderpuff reloads, which was no surprise. The recoil spring feels quite stout for a 9mm pistol. If there are aftermarket springs out there one day, I'll give the powderpuffs a try again. In the meantime, I'm quite happy to have a serious defense pistol geared toward real-life loads.

The FNS pistols are famous for their aggressive checkering, and I see why. I'm going to have to take down the top row of checkering on the backstrap to make nice with my desk-jockey hands. I like that the FNS comes with aggressive checkering; it's easy enough to take it down, less so to make it more aggressive.

Most of my other pistols are 1911s. The similar manual of arms was a selling point for me. The trigger, however, is not similar. I've heard reports that the FNS has one of the best triggers to be found on plastic striker-fired guns. That may be true--it's better than Glock or M&P triggers in my opinion--but it's atrocious compared with a good 1911 trigger.

There are two issues with the trigger: a gritty takeup stage and a very heavy break. I've read up on the gritty takeup, and I disagree with what most people think is the cause. It's not anything rubbing within the frame; pressing the trigger without the slide proves this. The grit, I think, comes from the interaction between the striker-block plunger in the slide and the plunger-pusher lever in the receiver. In this pistol, the lever engages with the plunger immediately and pushes it up over the entire takeup stage. The plunger itself does not feel gritty when pressing it up and down with a finger. But the interaction between the plunger and the lever is not up-and-down like in a Series 80 1911. Basically, the lever moves sideways and engages the angled side of the plunger to push it up. I'm not a mechanical engineer, but it seems like it would be hard to make this work perfectly smoothly.

http://cakesniffer.org/stuff/boom/FNS_striker.png

I might try polishing the interface between the two surfaces, but they already seem smooth. I think the issue is that pushing the striker block up like this creates a lot of friction between the block and the channel where it moves. Perhaps I can polish this area. I'll need to find a diagram for a detail strip, as the manual doesn't go past field stripping.

The reason and fix for the heavy break (it feels like seven pounds to me) is less clear to me. The sear-striker interface seems very well finished. Presumably the weight of the trigger press required for letoff is a function of the sear spring and the geometry of the sear-striker interface. I'd very much like to take this weight down to something more reasonable for a pistol with a manual thumb safety. There's no way Sevigny shoots with this stock trigger. :D

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