M*CARBO Brotherhood

Will The M*CARBO Rear Sight Pop Up?

My favorite thing about the sub2000 is that it folds to such a compact package. My least favorite thing is that it feels like a punch in the cheek bone with every shot. I have the rubber sleeve, recoilless charging handle, and buffer washer installed but it still is not pleasurable to shoot. I am looking for a taller sight and will not go to an optic because I want to maintain my favorite feature. I know there are folding options from Midwest Ind, M-Carbo, and Red Lion for optics but they are all compromises in my opinion.
For those that have one, does the M-Carbo rear sight pop up automatically when you unfold the gun. I see some people say you can adjust how tight it is so that it automatically opens but is that guaranteed or just lucky most of the time? Also is it high enough so that it solves the feeling of getting punched in the cheek?


@AZYooper I have the MCARBO rear peep sight and I can say that mine does deploy fully every time I unfold the gun. I would say mine is “snug”, with a little bit of tension/resistance felt if I decide to fold it flat manually, but I would not say it’s overly tight in any way. It feels solid, not a fan of floppy or loose bits on firearms. While the sight is taller (compared to the stock Kel-Tec sight that came on mine) and does move your cheek up off the tube a bit, I cannot say what the end effect is as I haven’t shot it since installation.


@AZYooper The MCARBO rear sight does pop up just like the stock Kel-Tec rear sight. The mounting screw needs the proper tension for that to happen. Figure out where that tension point is and Blue Loctite that screw at that point. As far as the MCARBO rear sight being taller that is not necessarily true and has been discussed many times in the forum. Kel-Tec has had two different height rear sights in the past and those comparison pictures are posted in the forum. No one really knows when the rear sight changed and even Kel-Tec dosen’t know there are two different height rear sights. The latest Kel-Tec rear sight is the taller of the two and is the same height as the MCARBO rear sight.


Try that muzzle brake too.


I just installed the MCARBO rear sight on what was a gen 1 upgraded to a gen 2. It also has the rubber tube.

I didn’t check the height but I can say that previously I had to really bear my cheek down to see the sights. Not so anymore, it is perfect for my eyes now. Unfortunately I have not shot it much but the little bit I did I thought it felt much much better to the cheek.

After much debate to spend money in a new rear sight it optics I am very glad I went with the rear sight first!

I’ve never been a fan of a muzzle break. Only have one and it’s on a 14 inch 7-30 waters which gives me a headache even with double hearing protection lol

But I have an order in now for a muzzle brake and a two finger bolt handle. I don’t think there’s much S2K left for me to buy from MCCARBO :joy:


Thanks for the info on varying height from the factory. Since I bought mine in May, I assume it is tall already. I found a post on the subject but didn’t see any photos or measurements that would allow me to confirm it is tall. I am not going to drop money on a new sight unless I am sure it addresses my cheek thump issue. I wish they would sell a set (front and rear) that was intentionally taller to address this issue.


Since my muffs don’t work because they hit the tube I have to use less effective plugs. Seems like a trade off between hearing and cheek pain. Since hearing loss is permanent, I will take the cheek pain. Now if there was a tall enough sight so that it didn’t hit my cheek and my muffs didn’t hit, then I would be interested in the brake simply from the cool factor and making it more fun to shoot accurately fast.


See the photos at the following posts and read the discussion in the posts surrounding them.
Good Luck.


Thanks for pointing me to that thread. It appears my “new” rifle has an “old” sight in it. Best explanation is the supplier made a change without KTs knowledge so they are all mixed together at KT under the same piece part number.
I acknowledge the difference in height is small and likely won’t solve the issue but I have learned that even the smallest clearance can at times make huge differences.
I am stuck as to how to proceed. Ordering a new sight from KT may only cost a few bucks but I may get the same sight I already have. Ordering a new sight from M*Carbo will get me a different sight but the small difference may not solve the issue and waste good money.
I still think someone should make a matched set that raises both sights. I will gladly take a Dremel tool and make space for a taller rear sight so that I can still fold it.


@AZYooper KT actually denies ever changing the rear sight and as you’ve noted, there seems to be no temporal pattern as to which firearm gets which sight. My S2K purchased in August 2018 came with the “old” sight but two replacements I ordered a couple of months later were the “new” style. I think the odds are good that any replacements you ordered would be the newer, taller ones. The difference is very small though.

One other thing you could try at minimal cost is to convert a $5.00 replacement KT peep into a notch sight which would raise your sight line considerably. See the following post.


Going to get the Mcarbo rear sight but in the meantime would like to do the rear sight modification so that it folds down and forward.

Would like to cut the tips of the dog ears without removing the rear sight. And would like to do so so that the rear sight still can pop up by itself or with a small flick of the finger. Any tips? Would it be easier to cut the dog ears with sub partly unfolded? Best tool to use?


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When I did mine, I used a small pair of side cutters. I did it without dissasembly and it autodeployed but could be pushed forward and down.

When you look at the ears that need trimmed, my advice is to remove as little material as possible with each cut until you can push it forward with some resistance - cut too much and autodeploy is lost.


@blowback It is super simple to remove, this way you can snip off just a tiny piece , then try it. I got it on the first cut. If it still won’t fold, snip off a little more. You should be able to snip off just enough to let it deploy when you unfold the sub but you can push it down with just a little bit of pressure. I used a small pair of wire snips.
EDIT… I should have read the answer from @Dred. What he said :joy:


Thanks guys. With your advice I’m going to do it. Forgive me for the basic questions but since I don’t have the rifle in hand how does one start cutting the arms as low as possible without removing the sight or cutting the material around the groove that the arms rotate in?

Fold the rifle and the arms become accessible?

Thx again!

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Weill Cornell Medical College
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I have been busy with other things. Finally got around to ordering a new sight from Kel Tec in hopes of getting a “new” one. Unfortunately both that arrived were the “old” style. I will do the notch mod instead and have a spare to experiment with. Thanks again for pointing me down that path, it is worth the try.


@AZYooper Let us know how it works out.

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Converting a factory peep to a notch made a positive difference. It no longer bruises my cheek. It is amazing how a tiny difference made a big impact. I was a little concerned if the front sight would have enough adjustment to compensate for the taller rear and it did. I think I was near the end of the adjustment range as the indent was not as firm. Overall I am very happy. Thanks again for pointing me down this path.


@AZYooper Glad it worked out. Can you post pics?