M*CARBO Brotherhood

Finished the Install & Upgrade - Tips and Experience

Well, I mentioned in another thread that I recently purchased two S2Ks, a 40 Stock and a G19 M-Series. I had not taken the 40 to the range by the time my M-Series arrived. I did not discover the M-Series until after I got the 40, and as hard as they are to find ANYWHERE for under $800 for stock models (have you seen what they go for on Gun Broker :flushed:) I grabbed the 40 at standard retail when I saw it. My “warrant” (Retired) side arm was a Sig P226 .40, I have about twelve Sig mags for it and thought the S2K was a perfect bug out companion.

I also used to carry a G26 in an ankle rig and a G19 in either a shoulder holster or inside the pants holster depending on the time of year (my agency did not like us having weapons exposed to the public in plain clothes). I had been trying to get an S2K in the G19 format for what felt like forever. I got very lucky when I saw them pop up on MCARBO and snatched one quick like.

All I had to do was pull the trigger on the M-S2K and it was over. The mushy, heavy, horrible trigger on the 40 ruined the whole gun for me. I was actually kind of pissed. Misplaced anger, I know, but, C’mon man! If I had waited, I could have gotten two M-Series and lived happily ever after. So, I made the decision and bought ALL the upgrades except for the scope mount. It looks awesome, but I am very pleased with my system, it is not as fast as MCARBO’s, but faster than the Midwest offering. I also like the flexibility of easily removing it for using just the sights (more on that later). All I have added to my M-series is a new front sight post, the RDL (rapid release) and the butt pad.

The wife took the twins to Mexico for a week, so I saw my opportunity to sit down and put it all together uninterrupted. Here’s where I started. You can tell the .40 is the bottom S2K.

and the “project site”…

I put the M-Series aside and got set up for the big install!

As far as the install went, I had watched the video, twice before starting a week and a few days before. I wrote down all the tools I might need to buy and had it all ready to go. I had no problems at all. I went slow and smooth (My steel coach used to drive in our heads that, “Smooth is fast, hurried is slow”). Paused the video and rewatched something if at all iffy. I also did all the suggested polishing. The two most difficult parts for me were…

  1. Getting the pinned doohickey on the end of the recoil spring. It was more figuring out technique than actually difficult. I can see how someone with arthritis or weak hands could have trouble with it. My suggestion here would be to get a 2x4 and cut about 4 to 6 inches off of it. Drill your 3/4 inch hole in the middle and then follow the video (the new video on the charging handle install). I did the method Chris used, but think having a thicker block would give greater control over the whole assembly.

  2. The butt pad. Once you get the holes drilled, putting it on is easy. Getting the holes lined up exactly is not at all easy. The entire process is awkward and doomed for failure if you try to rush it. Even taking my time, mine aren’t on perfectly. I asked my daughter (the one that had to stay for school) to look at it and she didn’t notice the slight overhang on one side. I really believe that MCARBO, since they do these regularly, could make a stick on template for the butt with precise locations to drill the holes. This would save an enormous amount of time fiddling and trying to hold everything in place while trying to mark the holes. Heck, I would have paid and extra 5 bucks for that! All in all, since they’re my guns, I wanted them perfect, not almost perfect.

Done with the 40

On both weapons, I installed Hi Viz front post sights. It was an easy swap out. These sights have a small fiber optic dot that works well in daylight. If you are like me and like to shoot with iron at times, or if your batteries die in your red dot, these are a nice and affordable addition. The next upgrade I would really like to see from MCARBO is a folding front sight. I have seen the Red Lion, I know people like it a lot, but I’m not convinced and am positive that Chris and his crew can come up with something better. I would rather have a foldable front sight and have the flexibility of using a higher RDS riser and not worry about trying to get the two to co-witness. With my scope system, a higher riser would get my face off the tube and provide a better field of vision.

Overall, I found the project somewhat of a challenge because I’ve never done anything like this before, but I am a big DIY guy with lots of tools and gun accessories.

One tip that saved me twice. When working with springs and little jumping pieces in the past, I would cut some mosquito netting into a 3’ x 3’ piece and drape it over the parts I was working on. Easy to see through and stops unwanted escapees. While cutting through Walmart, I went through the fabric area. I noticed a roll of the material that was really see through. The stuff they make the frilly part of a ballerina’s tutu out of (if you’ve had daughters, you probably know). This stuff was CHEAP! I got a yard of the stuff for about $2. It is folded twice also, so I got a shload of the crap for future projects. Worked perfectly and saved a flyer on me and is a lot cheaper than cutting up good mosquito netting. I also used it to drape over the parts while I was polishing them. It did a great job at stopping dirty polishing compound from spraying all over the place. Just don’t let your Dremmel touch it or you will have it wound around the Dremmel bit like a big cotton candy (speaking from experience :neutral_face:).

I highly recommend that you try to do this whole upgrade to your S2Ks and I actually enjoyed the whole thing (except for the 20 minutes on my 60 year old knees looking for a screw I thought I dropped on the floor, but was really stuck to my magnetic screwdriver. F Bombs galore!). Save up and buy everything at once, set aside a half a day and go to it. If you don’t have the carbon screws and grip pins, chances are you will tear up the aluminum crap pretty quickly, if not the first time you take it apart.

My biggest question now is… Do I tear my M-Series down and polish the parts they didn’t? I can see that neither the feed ramp nor chamber were polished so I’m sure the hammer and sear weren’t either. It is sort of a compulsion with the S2K. If there’s something you can do to make it better, you want to.

Double companions. Very pleased. Now I have to decide which goes in the car and which goes in the bug-out bag. Oh, life’s tough decisions!



Nice job and Great Post!
Curious about any additional details you can provide on the new front sight post


Excellent write up :+1:


I recommended that MONTHS ago. I’m not sure if @ChrisNelson or someone on his staff monitors the board, but if someone can make a list of requests like this one to talk about in their team meetings, it’d be a boon for their customer service.


It is not perfection. But, IMHO, I think it is at least better than the stock sight. The fiber optic dot is pretty small, so don’t expect a glowing beacon of death lighting up in the center mass of your target. It is bright enough in the outdoors to make sight acquisition faster, or indoors with good overhead lighting. You still need good sight picture, focus on the front sight, yada yada. The RDS has taken away so much of what made shooting a skill and a hobby at the same time. Don’t get me wrong, I love the red dot technology and have them on all three of my PCCs. It just isn’t the best place to start for new shooters (not saying you are :wink:).

I like my iron sights because it teaches good shooting discipline. Most people that start out on fancy guns with fancy glass are just almost always doomed to be adequate shooters at best.

I started all of my kids out on single action, 22lr revolvers with crappy notch sights.


I bought them their own that is their first gun to keep forever. How to be safe, shoot it, trigger pull, sight picture, break down, cleaning, you get my point. Once they had that down, I moved them to this (Some prefer bolt action, but new shooters engage more with the “coolness” of a lever action. Again, no glass. To this day, this is one of my favorite toys to play with. Cheap ammo, accurate, can plink all day, and Henry makes a solid feeling, sturdy rifle that just feels good to hold.


Once proficient, then an intro to optics and auto feeders was the next step.

For a rifle with basic optics, I love the Ruger American Rimfire series. One of my favorite rounds of all, rim or center fire, is the .17 HMR. The round itself provides inherent success and accuracy. Extremely fast, it remains hyper-sonic well past 200 yards. This is a really good gun and round to learn the basics of scope shooting. I don’t use more than a 1x4 scope, as too much magnification can cause more problems than help to new scope shooters.

I have always really like using the Browning Buck Mark Series (formally the Challenger) for teaching newer shooters how to use an auto-feeder. Accurate, reliable and fun little guns. Great for a forest trek sidearm collecting squirrel brains for grandpa’s dinner treat. The .17 just makes the squirrel explode. I’ve seen it, isn’t pretty.

After that. I am a big believer in starting new shooters that are moving up to center fire with double action revolvers. Revolvers (see the 22 above) force a shooter to be more deliberate about everything… trigger squeeze, sight picture, surprise shot, reliability, etc. I lean towards a S&W 686 or a Ruger GP 100. Both are comparable in price, but some say the triggers on the Smiths are a little better and the finish is cleaner. I love them both as I was issued a CS1 (a 686 built to the old US Customs specs and when we switched to autos, Obama had the service smelt them all. I wanted to buy mine). I own a GP 100. I don’t notice much of a difference, but have never had the two together at the same time. I teach “one round at a time” and why the mechanics of shooting are more important than what you’re shooting. I’ll take shot placement over foot pounds any day of the week. Wouldn’t you? Revolvers make you make every shot count (For the record, my concealed weapon of choice is the Springfield Hellcat in 9mm). I also think that this is the ideal handgun for the inexperienced gun owner starting into the world or home defense (different topic, I prefer my 870 for that). You pull the trigger six times, it goes bang 6 times.

From there? When I’m always asked, “What gun should I get?” My, answer, “Research and try a bunch then buy the one you think is going to save your life the best.” Confidence in your equipment is way more important than someone else’s confidence in your equipment.

Wow. I really got off track. I hope I answered your question early because I went total squirrel on y’all! LOL



LMAO… Helleva reply! Lots of good info :+1::metal:

1 Like

Well. I took out the rebuilt 40 today and it shot flawlessly! Obviously a relief since this was my first venture into anything like this. I have to be honest that I was hoping the gun wouldn’t explode on the first trigger pull. Everything was as it should be and just as good as my M-Series (it should be since it has EVERY INTERNAL PART they make :wink:).

The only difference between the two is that the 9 has a Sig Romeo 5. Since I couldn’t afford two of those right now, I had already purchased a Bushnell TRS-25 for the M-Series, which got traded out for the sig sight. I put the Bushnell on a medium riser clamp-on and mounted it as far back as I could on the 40 and off to the range. The medium riser with both the Bushnell and Sig sights give a very close co-witness with the front sight and the foldable rear sight is a bonus for shooting a RD. I have to say I was VERY impressed with this little RD sight and it held zero the entire day once sighted in. It’s waterproof, shockproof and nitrogen filled for anti-fog. They are about $70 on Amazon as I write this. My son and I put 210 rounds through the gun without a single issue. None. Both S2K and the Bushnell sight performed beyond expectations!

I wanted to sight in at 25 to start with. With no catastrophic failure occurring :pray:, the first round went down range without a hitch. The range scope showed that there was no hole on the paper :flushed:. I mean WTF? I’m at 25 yards for God’s sake. Three more rounds with the same result had me “not happy”! I locked the gun well into my shoulder, settled into some sand bags, got a nice sight picture and then looked up over the sight as I launched another round and watched it impact the berm by at least three feet high and at least a foot wide right. The range gods were smiling on me because after some really “aggressive” cranking on the adjustments, I actually got on paper for my next three rounds! After extensive tweaking, I got that sight right on. I took it on and off the S2K a few times and it held zero really nicely. By the time I was finished, I was consistently shooting sub 1 inch three-shot groups at 25 yards. Recoil was minimal for a PC carbine as was muzzle rise. I have the fat charging handle, the cherry lifesaver and the full size muzzle break on the weapon all of which made for a fun and manageable shooting experience. One of the range masters saw my S2K and mentioned he bought one for his son, but noticed that mine had some “extras”. I showed him the pre-build picture (above) and the M-Carbo website. He was a good dude, so I handed him a full mag and told him to try it out. Just like EVERYONE, that tries the upgraded S2K, his eyes got big on the first round because of the difference in trigger pull. He politely (not necessary) cleared the gun after five rounds (because ammo is “precious” right now) and basically said I ruined his son’s S2K for him and that he’s going to have to place and order. I laughed and told him that I knew EXACTLY how he feels (see first post).

Now, I am really happy that I had purchased the 40 as a stock gun and took the journey of upgrading it myself. The entire experience was a new one in the world of barrel sucking and it has given me an even better understanding of how they work and a feeling of accomplishment and self-satisfaction. If you’ve been at all iffy as to wether or not to try to do the upgrades yourself, go for it. It’s well worth It on many levels, from the build to the end product.


I think the TRS-25 is a great sight, especially for the money. I just wish they would come out with a circle dot reticle version. If they did, it would probably end up on all my long guns.



I love the circle dot reticle and wish more manufacturers would offer it, not just Bushnell. Waiting on the new Burris Fastfire IV which will have four switchable reticle options…


cool, seems to be a demand for upgrading these locally as well, talked with two owners who want all the upgrades but won’t do it themselves, so I’m doing them for them, one may take me up on my offer of coaching him through it and come over and do it with me to learn a bit. The S2K is really easy to tear down to the last little part and put back together, and the Mcarbo videos make it all the easier too. Most people lack the basic tools needed, which isn’t much really, a 2.5mm hex type (x2), 3/32" blade screwdriver and needlenose will suffice if one doesn’t want to fully equip a toolbox, which is just another compulsion with me.


Fell in love with it on Eotech. Enjoy it on Holosuns. Also enjoy a reasonable facsimile on a couple of my LPVOs.


I am beginning to think a quality LPVO is an acceptable substitute for a red dot. At 1x it pretty much functions identically while also providing a low power scope of 4-6x. Weight and eye relief seem to be the major problems. If someone could break those barriers at a reasonable price point they would really have something.


Eye relief at 1x is extremely forgiving. I run a Vortex Strike Eagle 1-8 on my 223 Wylde AR and I’m very happy with it. It’s not a bump in the night grab for me. IMO the real issue is lack of shake awake. All of mine are turn the power dial to your desired brightness setting to light up the reticle.

I also run cheap LPVOs on my 22lr AR and my 47/70 lever gun.

1 Like

LOL! That was half the fun. Buying brass punches, a torque wrench, dedicated needle nose and screwdrivers in the new “gunsmithing” toolbox. Gotta make sure you’re “ready to to a build” when thee opportunity hits!


I concur, my gun toolbox is well equipped and adding more weekly.
Layered, plastic bin in top has more, under the block, hex drivers and micrometer.
Under punches is 3 or 4 selections of needle files, just can’t have enough.
I like this Apollo toolbox but it’s getting small !!


As my kids would say, “Knohice” (Sp? Weird way of saying nice)

1 Like

I think we all have a dedicated Gunsmithing tool box :grin:

1 Like