MCarbo FN509 spring kit = awesome!

Finally! The CV19 situation has made life miserable for many of us, and ammo much more expensive. Got a change to sight in my FNS-9 with Holosun HE507C-GR V2 and APEX trigger and a FN509 Mcarbo spring kit. Yes, the 509 kit works in the FNS-9 full size. Also added Trijicon suppressor height iron sights. Flawless through 150 rounds of 115gr. FMJ. The trigger and spring kit makes a huge and noticeable difference. Sighted in for 23 yards (the longest length available at the gun club). A pic attached.

The gun was built pre-2014, and I worked with APEX to get a new sear that makes the gun cycle properly. The sear has a notch in it. In case you’re wondering, the Holosun has the green cirlcle dot reticle. Thankfully it allows me to shoot with both eyes open since I’m crossed dominant eye. Can’t measure the trigger pull weight but it’s real light with hardly any reset. No, I did not put the sear spring in myself - work (slide milling, cerakote, red dot mounting, trigger and sear spring) done by Wright Armory, Phoenix.


Great review!!
That’s a nice looking piece too. :+1:t3:
Interesting information on the Holosun as I have a 507K on order, hopefully to be shipped next month.

Apex are good folks for sure, I have their kits in three S&W’s, flawless from day one.


@CACinAZ beautiful piece you got there!


What is the additional benefit of upgrading the mcarbo springs with the apex trigger? Currently have the apex trigger but thinking about upgrading the springs too. How light is the trigger pull with both upgrades?

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I’m getting ready to put the Apex trigger in my 509 tactical and was curious if you used the Apex trigger block to install your triggers? I’m hopping its not necessary for the install any input is greatly appreciated!!!

I did one for my buddy.
I used the jig to remove the pin and I would say that it absolutely necessary.
That pin is very tight and it has to come out of the frame perfectly straight.
It’s worth the investment.


How do you like your PMM comp? I was seriously thinking of getting one.

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