Which internal S2K upgrades are really worth doing, and by whom

Afternoon, I’ve done plenty of internal pistol and rifle upgrades over the years, but have decided to have Kel-Tec , and or M*Carbo do these upgrades to preserve the warranty. First off, what internal upgrades will make the biggest difference in the S2K? So far I’m considering doing the all in one pro performance trigger job bundle - $234.95, and the stainless feed ramp - $34.95. What other internal upgrades will truly make a difference, not only performance wise, but also for the longevity and strength of the weapon.? I’ve heard many say, don’t wast your money on upgrades, just buy a weapon that’s awesome to begin with, well it’s a little late now. I kind of look at it like restoring a car or anything else, I’ll never get the money back out of it, and am ok with that, plus I’m having a lot of fun throughout the process. Any thoughts On this would be greatly appreciated

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Internal? That’s what you need. External? Totally up you.

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Well, I’m pretty sure the all in one comes with the SS feed ramp. I know it used to.

There might a few odds and ends that don’t cone with the all in one, like the SS bushing. But I would need to look into that. Not sure anymore.

Most of us here have done it ourselves following a Chris Nelson video, not all that hard. But if your have the pros do it, nothing wrong with that route.


Thanks, I’ve done several of the external upgrades so far, but still have the rear fold down M* sight, and RL front to do. It sounds like Kel-Tec or M* will do the internal stuff, is there any price or other advantage when it comes to who does the work

Afternoon Jorge, what do you recommend for internal upgrades, and by whom, Kel-Tec or M*Carbo?
Thanks for your help

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Just send it to MCarbo and let them do their magic. Get the all-in-one with a flat blade trigger, add a folding sight, have them do the recoilless charging handle (the two finger one) and recoil buffer. Be sure to include polishing. Just do it all at once and be done with it because you’re going to end up doing it all anyway and this way they deal with it rather than you. It’s not as easy to mess with the S2K as an AR or something. In fact it gave me more problems than any other gun I own (regarding disassembly and reassembly).

But once you have all that done it really is a whole new gun. It went from a gimmick to a really fun and capable little carbine. The stock trigger absolutely sucks and it just felt like it was minutes away from breaking to me. Now? She’s solid and fun as hell to mag dump.

Other than that I like the MCarbo optic mount. I tried using 45 degree mounts but nothing seemed to hold up well. The mcarbo one holds zero. Even with my giant prism scope.

On the front I stuck on a really good hunting laser.

That think is sick. Sunny day it’s good for 25 yards. Clouds in mid day 50. Evening? Maybe out to 100. The best part, though, is you can twist the shiney end and open it up to become a laser flashlight that’ll light up a large area. It’s meant for shotguns so staying zeroed on the kel-tec is nothing.

My foregrip holds the switch and converts to a bipod. I don’t think they make them anymore, however. It wasn’t cheap but it’s very useful. Ran it on my AR until I decided to move the laser over and needed something smaller on the kel-tec.

The one thing I recommend over mcarbo is the butt pad. Look on Amazon and you’ll find one that’s really cheap and just slips on. It’s surprisingly good though.

I’m not sold on my prism scope so don’t go there yet. I’m keeping an eye out for something better. Maybe a small LVPO because I’m partial to optics. Sure I can use irons but I’d rather thread a needle with every trigger pull. Just my thing though.

I find this more fun… (Bipod on a table at 25 yards. .22lr. 25 rounds per target. First three shots on center target was zeroing it in)

Than this. (Shoulder fired AR at 50 yards)

The other reason I’m not liking the prism scope is the size of the darn thing. It’s reduculously big.

(On the bottom)

In order to fit it I had to get a small riser which also lifted it up. Overall it’s 3-4" above the barrel which makes it harder to hit dead center at variable distances. I prefer my optic to be as close to the barrel as I can get it while still being good for cheek weld.

If I were to design a rifle for precision shooting I’d likely put a dip in the stock for my face to nestle into and keep the scope as low as possible. I’d also figure out how to eject straight out the bottom or at least at a 45 degree angle out the bottom. Then again if I were doing precision I wouldn’t be using a 9mm round so there’s that…

Anyway you asked my opinion. I’m no pro shooter. I’m just range rat who likes to put them through the same hole at 200 yards to save on targets.

(That was 200 yards with my .223. the red center circle is 2" in diameter. Can’t find one with the .308 but the groupings are even tighter)


Thanks for all the info. Once I get most or all of it done, I’ll post a few pics. My wife helped me today attach the tool-less locking pin to my recoil spring, I did the compressing of the spring while she attached the locking pin, with two people it was a piece of cake😀

I’m only 1hr from the Kel Tec factory in Florida, so I went there to have them do all the upgrades last week, while I took the factory tour. It was an awesome experience! What a great bunch of dedicated people working there! They are all really into their craft, (and guns).

One of the upgrades I did was the Mcarbo trigger package upgrade. It’s a total package, has all the internals. I highly recommend them doing it. They only charged me $40 for everything, and we left with goodie bags! Just bring your parts or you can buy them there, they have a wall of Mcarbo upgrades!

P.S. I had them upgrade the front sight to the Redlion flip sight also and the Mcarbo fast deployment latch, I had issues, I posted all about it on this sight. I feel like I’m ranting about it, but I’m really not, I just want to share what happened so others know what to look out for.



That says a lot that they stock the MCarbo upgrades. Glad to see a factory working with aftermarket like that. Wish that happened more often in all industries. Reminds me of Shelby and Ford. Just makes the customer experience all the better!

Sounds like a great relationship, plus everyone wins

Personally we have a very reasonable young gunsmith who did mine. Charged me 50 bucks.
Did the kydex, washer for recoil, side cover (plastic) heavy recoiless pull knob and a few other things including lubing the gun for me.