M*CARBO Brotherhood

My new M-series

Today I received the Sub2000/G19 that I ordered from MCARBO.

Took it to the range with 50 rounds of Federal 124 gr FMJ and 50 rounds of Federal 115 gr FMJ.

Had a little trouble sighting it in. Had to move the front sight pretty far over to the right, which is apparently common with these guns. This creates an unusual sight picture where I can see the protective wing on the right side but not on the left- took a little getting used to.

Put on a Trijicon RMR with QD mount attached to the top rail. Very unstable, definitely did not hold a zero after taking it off and putting it back on. Ordered a MCARBO mount, it is pricy, but it should be solid.

Accuracy was OK, nothing to write home about. I believe groups will shrink when I get more used to the gun.

Recoil was a bit sharper than I anticipated, much more than my Just Right Carbine, but then again, it is about half the weight.

Reliability was so-so. Out of 100 rounds I had 8 malfunctions. New round would feed into the chamber with the empty stove piped (and often crushed) behind it. I’m hoping this will disappear after break-in. The bolt seemed stiff and gritty out of the box, I lubed it before I shot it, and it seems to be getting a bit smoother. Another brand of ammo might make a difference as well.

Looking forward to putting some more rounds through it once I get a proper mount for my optic. It will be a handy little carbine once I get the bugs worked out.


I used fine steel wool on the bolt, bolt head, and receiver tube to smooth them out and eliminate any grittiness. Run it wet the first 150-200 rounds. Stovepipes sometimes happen if the ejector isn’t straight.

I’ve had pretty good luck with a red dot/qd mount - is the forend tight, anything move when you flex it? I never had a problem with my front sight so can’t help you there.


The steel wool treatment is a good idea. The ejector looks straight, I wonder if the problem might be a combination of the rough bolt and lower powered ammo.

Fore end is tight, but if I grab the optic, it will move a tiny bit. Not too worried about the irons as they will be mostly for backup use. And they do work, just need to get a bit more practice with them.


The recoil spring may be a little stiff too until it gets broken in. If your ammo is standard velocity, it should cycle without a problem, but if the bolt doesn’t go back fast/far enough to eject the empty… Mine also had a burr in the receiver tube I had to file down, along with needing to bend the butt-end of it out some so the bolt and bolt head could be removed.

Check to see if the rail is rounded on top. That would let your optic rock.


Like @phuzzy42 said, take a file to the pic rail as they are notorious for being rounded. Filing off the “hump” will allow an optic to seat firmly. Go easy as it doesn’t take much. That said, you will like the Mcarbo optic mount. The main downside is the additional space required for storage when folded.


I think phuzzy may be right about the standard velocity ammo not having quite enough power on a new gun to eject consistantly. Hopfully smoothing out the bolt and putting more rounds throuh it will resolve that issue.

The top rail isn’t quite flat. I’m going to try the Mcarbo mount, if I don’t like it for some reason, I’ll flatten out the rail and try the qd mount again.


You can loosen the nut that holds the sight in place and rotate the sight as needed to better center it. Had to do this on all my S2K’s.

Feel inside the bolt tube where it is cut out for the charging handle. Mine had burrs on it inside the tube. Use either a dremal or jewelers file to remove the burr and it should eliminate the bolt drag thats causing your jams.


My front sight assembly seems to be on straight, I guess it could be slightly canted to allow the sight picture to be more centered. I have the muzzle brake in front of the nut holding on the sight, is it hard to get the brake loose?

I’ll be breaking the gun down this weekend to smooth things up a bit, I’ll be sure to check for burrs.


My mseries had similar gritty feeling for the first 150 rds, then after 2nd deep cleaning is pretty smooth. Like others i plan to polish and smooth out the bolt and tube. The burrs sliced my hands up pretty good my first time out, until i found them all.
Its not hard to loosen the brake, but the locknut behind it needs a super thin wrench to snug it back up straight.


Tore the gun down over the weekend. Didn’t find any burrs, but steel wooled everything down. Feels much smoother now. Added the Mcarbo sight mount and single point sling mount.

Fired another 50 rounds today. Having a solid optics mount made a huge difference, was able to get the RMR zeroed. Had 3 failures to eject, using same ammo as last time. I need to try another brand of ammo and run a few more boxes through it, hopefully the malfunctions will go away.

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The thing that worries me is the 8 malfunctions out of the first 100 rounds. I can understand maybe one or two at the very beginning but as this keeps happening, I would have to send it back to Kel-Tec for service. I have had my Sub2K Gen 2 for over a year and I know I have almost 1000 rounds fired and I have had NO Malfunctions at all. I use only 115 Grain 9mm ammo and have been shooting 50 to 100 rounds per week. I don’t know much about this M version but It seems to be an upgraded gun and maybe more expensive. Just my Opinion but I would send it back to Kel-Tec and have them check it out! Good Luck


It is concerning. I do want to try a couple other brands of ammo in it to see how it does. If problems persist, I will be contacting Mcarbo.

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Success at the range today. I shot 50 rounds each of 4 different varieties of ammo, including the stuff I had malfunctions with before. Everything worked 100%.

I have a theory of what happened before. I was shooting at an indoor range which is set up pretty much for handguns. The table you shoot from is fairly narrow and not very deep, so getting a solid position is a bit problematic. The first couple times I shot the gun, I was pretty close to the right side of the booth, next to the divider wall. Since the gun ejects pretty much sideways, a believe that the empties may have ejected, bounced off the divider wall straight back to the ejection port as the bolt was moving forward to chamber the new round.

Anyway, it all is good to go now.


Highly unlikely, not enough time for that to happen unless you were less than 1 inch from the wall.
Glad your not having failures, just advising to still keep an eye out for the true root cause.


I’m with Stircrazy on that one. Winning the lotto odds on that one!


Man. I would pay to see that! And more than once? Crazy!



I didn’t have the firing issues you guys have had.
But I noticed the poor finish on these first thing…. So I took it apart and used some 1200 grit and rem oil on all the moving parts (like the bolt and the inside of the tube, etc.)
and it’s smooth like Butta’. I can’t stand a gritty metal finish. I clean and oil my stuff every use so it stays nice and clean.

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