M*CARBO Brotherhood

Just Ordered the New Locking Pin

Now that would be fun !


I had the same thought , but I just put mine in and it took me less than a minute. Super easy!


I was hoping for a heavier spring to go with the pin.

A guy on FB used his buttstock to hold the spring instead of a bench block. Not sure what his name is on here, but all credit goes to him.


Springs and guns can be like “Goldilocks & the Three Bears”. Too much k-factor; too little; just right.

The manufacturers make these “just right”, but when you put a mod like this on the firearm, there can be a “loss of tuning” in the motion of the machine. I’m glad we have a forum like this. I haven’t seen anyone say they’ve had a problem.

With that said, I not only bought a spare spring (from Kel-Tec), but also two factory charging handles. I did that as a precaution/contingency. I also did it in case I messed up the spring alteration. From what everyone is telling me, it isn’t that hard.

I also saw someone used the hole in the butt stock as his bench block. (Thanks DocA!) Great idea! That solves one item.

A true “firearms hobbyist” likes to tinker with things like this. It’s one of the reasons I like the hobby. Tinkering with firearms takes a lot less room and resources than tinkering with motor vehicles. Just my opinion! (Some of you MUST like tinkering with cars! That’s a whole nuther thing for forums elsewhere.)

Just so you know (I don’t think I mentioned this in my original post), I have broken TWO factory charging handles on my Kel Tec Sub 2000. The first time, it broke because the charging handle lock sliced the handle every time I used it. After a “death from a thousand little cuts”, it just broke.

The second charging handle broke after 1000+ rounds; just from cycling. Let me know if you (or anyone) have had these problems. Moreover, I hope this problem doesn’t crop up with the MCarbo modification. My guess is that MCarbo knows about this and has chosen materials that are more robust.

The Sub 2000 is a fun firearm to shoot. It deploys faster and is lighter than its Ruger competitor. It is also better balanced. I have also found it a bit delicate. These 3rd party modifications can (I hope) eliminate some of the “weak links” in the machine.

Thanks for the comments everyone!

C ya,



Mine broke a couple weeks ago just from cycling. It’s a known problem and one of the reasons MCARBO makes their own replacements, and yes, they are more robust. Keltec makes their parts just good enough in order to save a buck and their QC isn’t the best either.

I’d have been willing to pay them more for a higher-quality firearm but instead paid MCARBO to bring it up to snuff. I don’t have a problem with that but my PMR-30 had more than one issue too, so I’m not keen on buying another Keltec product.

That said, the S2K is fun to shoot and wicked accurate, along with being a great gun to put under the truck seat or in a backpack, and with a couple fun sticks, you have a good afternoon at the range.



Just watched install video. Took my part out of my mailbox on the way upstairs. I’ve got a new recoil spring coming from Kel Tec so I can add it and an old style handle to my expletive deleted kit.

I expect I’ll never go back, but I’m gonna minimize my down time if I gotta.

And, I rub’d a couple brain cells together. The recoil spring assembly is a $10 part from KT. I bet a lot of us are time crunched enough that we’d drop an extra $20/25 on the charging handle if the pin end was pre-installed.

You may also have a market for extra or reduced power recoil springs - least I think I read that a couple posts back.


Got mine yesterday and installed it without using any block. Took about 1 hr and
was like pushing a springy rope trying to compress the spring Not easy at all.
Use a block and save about 50 minutes and your sanity. : )



Just trying to get a visual in my head on that one. :thinking:


Got mine yesterday and installed it. Since I was already practicing on the spring with the regular end caps, it was fairly easy. That cap CAN come flying off in a hell of a hurry if your not careful. Wear your eye pro like @ChrisNelson says.

All went well until I apparently turned into an idiot re assembling the firearm. Try as I might, I just COULD NOT get the damn thing to locate into the hole on the charging handle. No matter what, it would not go (yea I know, put some hair around it). Started getting ticked off at Mr. Nelson for making it look so easy, again. After many attempts I realized that when your upgrading a part… sometimes you need to remove the part you are replacing. The old style locking pin was still in the bolt extension. Went together quite quickly and easily after I removed it.

Love the new solution. Just take out the pin it’s meant to replace before you reassemble. It will make you life much easier and you won’t feel like such a jack ass.


We’ve all been there man in one way or another!:joy:


Here’s your sign. :grinning:
I actually almost did the same thing.


Installed new pin on Monday, with help from a friend. Then I had a idea ( here hold my beer) tried to build a tool for installing. Key word here tried.

was working until the Allen wrench bent and the clip let go, (LOL) so I did another one by hand with two Allen wrenches and just compressed the spring. principal is there just not the wright parts. C clip also to thin, it bent also. On the bright side only have one more to upgrade, My old install tool, Acid brush, with brushes remove and red line painted , allowed easer alignment, with a little lube.


Got mine today these a very easy way to clamp the spring down, remember a spring will act like a bolt, put the supplied allen key between the 2 parts like Chris said grab the spring and spin it round and round. because the allen key is held in place the spring will slide past the allen key tightening as it passes it. its that easy. no fuss no muss. I was able to get over 1/2 space between the spring and the pin with little to no effort. No tools needed!!! Then pop in the new part and twist the other way less than 1 minute complete time spent…

I hope this helps everyone.


David AKA Tintrain1


Genius! Yes, that’s gonns help; Thanks.


Super fast shipping and it’s been here all week but didn’t take time to install. Got an email yesterday asking if I was happy with it… decided to find out, so installed it (with concern, I have severe arthritis).

All I can say is it went very well and didn’t take very long. Can’t say it was super easy but I was able to compress the spring enough to the replacement was easy (thanks to the great video and how Chris explains things).

Only issue was after I got it all back together, I forgot to install my red recoil buffer lol

Also as lucky as the old locating pin was about to fall out of the bolt when I went to install the spring.

Just take your time and don’t get in a hurry as I did and it’ll be a fun quick upgrade.

Thanks Chris for the video and all you do.

Last thing, I had the 2-finger bolt handle on my 40 bc of arthritis. Decided to order in the recoilless bolt handle to see if it make any difference in the recoil. Haven’t shot it but noticed that there is a big difference for me and I really like the 2-finger.

Have a pair of NIB 9s w/consecutive SNs for me and my son just waiting to get mcarbo’ized


@tinktrain1, I tried the twist method you mentioned and couldn’t get the spring to twist at at all. I must be missing something here. Did you compress the spring first then insert the Allen wrench before you started the twist?

I’m having a hell of a time getting this little piece where it’s suppose to go. I’ve got arthritis and just don’t have the strength in my fingers anymore.


NO… twisting the spring will compress it for you…


@tinktrain1, once I figured out that I needed to hold onto the allen wrench while twisting the spring (duh on me) I was able to get it done in a minute. Thank you for sharing this helpful advice. :+1: :+1:


No Worries, thats what the M*CARBO Brotherhood is for the sharing of good info, it’s all about the guns.