I had time to hit the range today but before I did, I shortened the RDO mounting screws and got all of that situated/secured. Drove out to the range and brought the LTT along for comparisons. I put about 200 rounds through the FN and it honestly felt gratuitous to shoot more than that. There was a tinge of guilt given the ammo shortage.
I had exactly two failure to fires, both ammo related. Other than that, the gun functioned flawlessly. The Remington 40gr. cycled fine even with the extra weight of the RDO.
The gun did loosen up. After the range session, I cleaned it thoroughly and re-lubed it and it seemed to be not nearly as tight and the slide seemed to articulate more smoothly overall.
Recoil on the grand scheme of things is just not there. I consider myself a rifle guy and I'm not nearly as good with a sidearm. The FN is just stupid easy to shoot and given that it's a full-sized gun, it's easy to get a good grip and just drill an entire mag without much effort.
Transitioning back to the LTT, there's noticeably more kick so I'm not sure, as a training tool, how the FN is going to help my situation other than being able to present and find the same red dot (Holosun on both). It did cause me to re-examine my grip and I feel the light on the LTT is actually hindering my grip vs the FN.
The other big difference between the two is trigger reset. Granted, the LTT, which I purchased from Langdon with their trigger job, pretty much sets the standard. I found myself having to mentally let the FN's trigger return further to fire the next shot. The LTT's trigger resets with about a mm of travel and I'd guess the FN is 4X as long. So it's a definite mental exercise. I found myself not being able to fire the next round a few times as I'd not released the trigger enough to reset.
Love the texturing on the FN. I read a lot of reviews on the 509 and how some complained the grip texturing was too aggressive. I don't see it but maybe the extra kick makes it annoying. Dunno. Not a problem on the 502.
At the end of the range session, there were two flaws that stood out. First, the FN has a small window on top that indicates if a round is loaded. Unfortunately, gas also jets up out of that small hole and onto the front of the RDO. I didn't necessarily notice it while shooting but examining the gun at the end of the range session, it was very noticeable.
The second flaw is this thing should come with at least three 15 round magazines (where allowed) or even a much longer extended mag to hold 20 rounds or so. I'm sure the aftermarket will come up with a solution but it's so easy to burn through a magazine that more than one 15 rounder should be included. It's easy to reload the mags (unlike the Beretta which is a PITA without a speed loader) and extra magazines seem to be vaporware at the moment.
I did briefly run over to the neighbor's house to compare to the Walther. I'll say the Walther feels a fraction more substantial/precise but not enough to make any sort of a judgement. I'll have to shoot both back to back.
Closing notes, no regret in purchasing the gun. I'm a modaholic so it'll be interesting to see what the aftermarket comes up with. I'd like higher capacity mags and a shorter trigger reset. I also need to order a silencer and will likely go with the OSS Rad 22 as I've had such great success with their suppressors on other platforms. The catch 22 is that it's a 22LR and really, how much money do you want to throw at it?