M*CARBO Brotherhood

Front Sight Post Upgrade



anyone taken the time to figure out exactly how much of an increase (how many clicks) it takes, on the front sight, to accomodate a rise in the rear sight?

so, for example, mcarbo says their folding rear is .08" taller than stock (though i wonder what the heck this means…yeah, i’ve called etc but no answer…and guys here have been kind enough to explain and illustrate the different (original gen2 vs revised, and other types) heights of the sight picture or at least aperture, to get a good idea of what’s involved.

anyone, has anyone done the math to say that , for instance, .10" rise in the rear = x many clicks of the front? is it as simple as using the MOA of the front clicks /elevation at distance, to equal the rise in the rear? i’m thinking yes?

why? i’m curious if i’m going to run out of elevation adjustment on my front when i install the ‘revised’ gen2 KT rear. (yeah, i know, trial and error, but i wanted to broadly avoid finding out at the range).

Postscript: the more i think about it, no, it’s not as simple as inferring from the MOA per click; not


After the installation of the notched sight it was hitting way high. While at the range I didnt have time to make adjustments to see if the front sight would go up high enough to get back on center. So I came here and read this discussion and decided to just order a taller front sight. Here is the one I ordered and am now back on target. I also painted the tip with some florescent orange nail polish like a previous poster did and makes a huge difference at picking up the sight with your eyes.


interesting. so you don’t actually know if the stock front would have raised enough to accomodate the notch’d mcarbo?

ps, was the front installation with this piece an easy remove/replace?



No not positive, just went off multiple previous posters comments saying a taller front sight is needed. Plus I wanted a sight post with the little ball on top so I could paint. And yes just push down on the detent then unscrew. Just be careful not to lose the detent and spring.


thank you



with ALL the myriad posts on this ‘dilemma’, what if i want a steel solution (besides optical).

how about a seriously taller rear and front combination that work together. preferably a peep. (i thought i could use a notch, but with a different sight picture …ie, top of notch…but i don’t want that…i want a ‘normal/ pistol-like’ sight picture…ie, bottom), so that i think is out.

so what about an overall steel solution that actually works, front & rear? maybe raise cheek off the tube by , what, a half inch? or too much? maybe 1/4? any thoughts on a final both solution?


@500c If I were going to do it, I would cut and combine two replacement rear KT sights using a lap joint cut with a file (Google it) and plastic weld, install a taller front sight post and call it good for under $20. But there’s a problem with installing any significantly taller rear sight.

See that recess in the photo below? It is there for the rear sight to tuck into when the S2K is folded. The rear sight doesn’t fully sit in the recess, but it does need a small bit of that cutout for the gun to fully fold and lock. Obviously, a taller sight will not fit. You might be able to extend the recess with a rotary tool and a steady hand or you might find the plastic is so thin there that you expose the rear of the barrel.


aha, and you know, i thought of that, but thanks for reminding me. i wonder (duh) if that’s a big reason the aftermarket solutions are so limited? no solution for folding


i have an optics solution arriving today (for me, a simple red dot on a 45deg mlok, w QD rail…i know holding zero might be a challenge, but not a big deal fooling with it at the range or plinking, and it’s not a home defense gun at all). but i’d been thinking (since KT sent me the same ‘old’ rear anyway, why not just cut a notch in one (similar to your thought), revise my sight picture (to the top of the notch), leave the factory front, and call that quits


@500c If you intend to make your own notch, here is a step by step plan. The finished result will move you up off the bolt tube somewhat. I cannot say much about the front sight or anything else as I never shot it before moving to an optic. My son shot a few rounds and it moved the POI vertically a lot so it may require a new front post just like the MCARBO Notch.

The two-part acrylic referred to is actually JB Plastic Weld which has filling and elastic properties somewhat like Bondo and is a better choice for this than regular epoxy. Also in a later post, I acknowledge using a regular file to final cut and shape the notch instead of hobby files. It made it a few hundredths of an inch wider than planned but the job went much faster.



I’m not sure if it was more me being cheap, or more being too lazy to drive all the way to town for a part that was cheap. probably about 50/50. LOL
Either way, I made a two tooth one using a brass .308 Win case.
If I were to make another one however, I would use a steel case. The brass teeth bend easily after being filed down. The steel teeth would be rigid enough to hold their shape, even with rough treatment such as being carried in a pocket, rolling around the bottom of an ammo can, or on the floorboard of the truck.


duh, what was i thinking? :frowning:

here is something i posted in “front sight” thread. don’t know how to link to it (moderator?).

i had a stupid experience that i don’t mind sharing so others can potentially avoid this stupidity

i mounted a red dot on a 45deg m-lok. and tried to zero it (and yes, i was aware of the difficulties and methods necessary to properly center it, and compensated for them).

i went through 130 rounds! omg, how? each time i would carefully make adjustments for one distance (let’s say 15yrds at first), it would move at another distance (let’s say 25+yrds). and the adjustments for the longer distance grew greater. and dare i say, more unpredictable?

what the heck was going on. only this morning did it dawn on me (shoulder and face aching ;))…the red dot is out-of-parallel to the bore! of course! in both directions, vertical & horizontal. slightly.

this out-of-parallel ‘opens up’ with distance. so when i finally zero at 15, out at 25+ it’s way off.

leading to the remarkable discovery lol that with an out-of-parallel situation, one can only zero at ONE distance.

why do i need to post in ‘front sight’ too? because, i’m the OP who had run out of windage with the stock sights (gen2) and I (and later KT too!) resolved it with a front sight rotation (so much so the front is now rubbing against the cutout/recess in the stock upon folding). so now i’m thinking: rotating the sight to solve this is folly too, no? this will create the analogous issue with steel, that is, the sight line will be out of parallel with the bore, and consequently only zero’able at one distance?

stupid? am i thinking clearly about this now? opinions?


i now see that a/ this is much more complicated than i thought (eg, arc of trajectory, etc) and b/ many others have faced and dealt with it with varying degrees of success.


As I read all this back and forth about the rear sight heights (we have had this discussion before) I can’t help but wonder.

Why not just pull the sights completely and either run an optic or a set of Magpul Buis sights? Thats what I did and solved all issues with eye-line, cheek weld etc.

Added bonus is it looks a whole lot “cleaner” and my acquisition is so much faster!

Problem solved! :grin::+1:


there are myriad posts on this and your solution. the rail, ayk, is crowned. i’m in the process of falttening it for this possibility too. i thought the m-lok solution which retains the steel and avoid conflicts with it, would be an excellent solution. but as you can see, it comes with it’s own problems

ps, with respect to the folding magpul’s in particular, do they interfere with folding the sub2k?


@500cc yes they would as does the red dot. Those of us who compete don’t care so much about the folding feature. In fact my next project is to convert mine to a take-down.

It basically comes to this. If you want a folder you are stuck with factory sight posts, a red lion forend, or some day an MCARBO folding mount. :disappointed:


What advantage would a non folding Sub2k have over a Ruger PC9? Or would the project just be for fun?


@Rekonn good question!

For me it comes down to weight and length. For the type of competitions I do it is mostly close range, lots of barricades, and even shoot houses/alleys. The S2K is the smallest, shortest PCC out there and is very nimble and quick.:grin:

I looked into the PC9, its a popular option but it is heavy, more so than the AR builds.

I am only fair to middling, but I still want to win, and when your cutting a corner you can acquire faster with a shorter weapon. Fractions of seconds count!


I only got 1 rifle thats a optic only ,thats a 300 winmag. crap goes bad a the worst possible time. the old 2 is 1 and 1 is a club style thinking… this meme says it all


@GOBLIN I had considered playing with a set of 45deg offset backup iron sights for the s2k. You would have to tilt the gun to sight through them of course.and they would no doubt prevent folding. My original thought was if they could be modified so they could be mounted on the bottom rail allowing it to fold.