M*CARBO Brotherhood

SUB2000 Upgrades: What Have You Installed & What’s Your Opinion?


Just but the bolt tube cover and recoiless charging handle. Looks awesome and hopeing to test it out tomorrow!


Thanks for the name. They have some great site posts. Ordered the orange triangle with the white night dot. Should help accuracy a lot


Think of it this way. When the round fires it releases a given amount of energy. Ill call it “force”.
The total amount of energy or “force” is released pushing the bullet forward at a given velocity and pushing the bolt backwards through the cycle.
If you shoot a stock gun, it will consume a specific amount of energy to cycle the bolt and the balance is applied to the bullet resulting in a specific velocity.
If you then increase the weight of the charging handle, it requires or consumes more of the available energy to force the bolt back and through its cycle…This reduces the balance of remaining energy or “force” applied to the bullet, thus reducing its velocity.
That can result in drop, as well as alter and/or adversely affect a bullets behavior and flight characteristics.

Hope that makes sense


In theory that may be correct, however in application it may not be … The theory is only actual if you have full burn … The primer sets off a charge by igniting the powder inside the casing, this creates pressure inside the barrel via gases that form and propel the bullet/projectile forward and out the barrel … however most of the time the burning of the power continues after the projectile has already left the barrel and the remainder gases dispurse into the outside air without any additional benefit of “push power” … which is the flash you might see after the projectile has left the barrel … having a heavy bolt is charging handle would not effect anything if you do not have full burn …


This also has a lot to do with the bullets you are using, weight, charge, shape ect … the distance from the shooter to the target … you are shooting a handgun round out of an extended barrel … all bullets have an arch to them once it leaves the barrel and will eventually begin to drop … different weight and shape projectiles perform differently at specific distances … if you are getting some drop, say at 50 yards using a heavier bolt, then try a lighter weight bullet or one that has a projectile with more aerodynamic flight, hollow point vs round nose … also you need to determine at what practical distance are you planning on using the weapon and at what distance it was designed to best function at …


I couldn’t figure out why i was shooting my 30-30 so bad. I’d sight it in then miss or gut shoot deer. Came across an article about harmonics and powder numbers on ammo boxes. I always used last year’s ammo to sight it in, then new stuff to hunt with, Remington core locks 150gr.
Went back out, shot old stuff dead nuts, new bullets were high 6"and right 9". Haven’t come across anything like that with my sub but I’ve split my extended mag between brands and can feel the switch on my shoulder and see the difference on the paper.
Some of it may very well been mental but i keep a pretty tight tolerance on my subs accuracy. Just going to the carbo rear sights opened up my groups a little from the larger sight line and that 1/2" drives me crazy.
Im using the stock handle and bolt with the recoil ring in my .40 and i can go through quite a few rounds on my shoulder with mi issues.


@GL9CK Absolutely. There are many variables that affect actual performance vs. theory on paper… Burn speed of the powder and barrel length as you said.
Other factors such as altitude, barometric pressure, humidity, ambient temperature, temperature of the round itself (setting in cool area or in the sun) , inconsistency of primer ignition or powder burn and other things all contribute to the actual result.


Using rounds that are designed for a hand gun and not a carbine seems somewhat flawed to me for the very reason you mentioned about burn time.
With the longer barrel it needs a slower burning powder to maximize its efficiency in combination with bullet weight, design, etc. I would think.


Exactly … I agree 100% … This is also why I don’t believe that adding weight to the charging handle or to the bolt will effect the performance of the gun or the trajectory of the

projectile within the max distance that the weapon is designed to be used for .. In fact I have the heavy bolt and the charging handle in my 40 cal Gen 2 and haven't notice any drop

in the trajectory of the round out to around 50 yards, which is about where I would personally place the max distance for this type of round .. 25 yards when using in a handgun ..

I have the charging handle on my 9mm Gen 2, I opted not to put the heavy bolt in it only because the recoil isn't that bad .. Have have the buffer in both, but only because it might

help save a little wear on the internal parts over a period of time ..


@Firedog that would be easy to test. If I anchor my rifle rest down, and make a solid latching attachment for the sub, to keep it solid in place.
I have some lead wire and flat sheet. I could cut pieces of different weights and wrap around my charging handle to see if there is any change.


All Things SUB-2000!
For now I’m just going to install the new feed ramp. I’m wondering if I have to take all the trigger springs hammer ect, out just to install the ramp. Thanks for your help


@Magboy Greg if you have never taken the sub apart I highly suggest you watch the M*CARBO “all in one installation video”. Once the grips are split the springs and other parts will become misaligned. You need to remove the receiver tube to replace the feed ramp which involves removing the internal parts. If you are going to get other internal upgrades in the future I would wait and do it all at one time.


It would, however it would only be accurate for that specific round of ammunition and at that specific distance from the target and under those same exact atmospheric conditions all the time …

It would give you a baseline .. But then you would also have to do the same test at different distances and under different conditions, with different rounds, with different weight projectiles that have a different

configuration like hollow vs round nose vs jacketed and non-jacketed and rounds that are manufactured by various manufactures .. Each one of these factors is going to have different results ..

My point is .. You are using a handgun round in a extended barrel weapon and these rounds are not designed to accurately hit a target that is 100 yards away or even one that is over 50 yards away ..

I am not saying that this can not be done, but the ballistics for use of handgun rounds is not recommended at great distances, which is why a rifle round is better suited for this purpose ..

One must determine at what distance is it reasonable to be using the weapon and then determine the type of round that is ideal for that purpose at that distance ..

If adding a heavy bolt of heavy charging handle alters the trajectory of the round that you are using at a specific distance, then changing to a lighter round or one that is more aerodynamic in flight

might be the way to go .. I haven't seen any noticeable drop in my shot placements at 25 or 50 yards using 185gr FMJ's ..  This might not be the case if I change to another type of ammo. I use these

rounds for practice because they are cheaper and I get them in bulk qualities ..


Totally agree.

For me, it’s only real value, would be to eliminate shooter error. If that’s not eliminated, so the gun can shoot precisely centered every time, then whatever it does is only an assumption that it is caused by the gun, ammo or conditions.
Trying different rounds and combinations would be futile at best without a known, stable beginning point.
I think 100 yrds can be achieved with the right round and precise, repeatable sighting.
I, like you, believe the handgun round is the flaw and its redesign is the key.

I also like the heavy rounds. For me (although I have others more suited, .223, .308, 30/06) out in the open desert, I would still like to have impact for larger game at the longest distance it is capable of.
Something I had proposed, before joining Mcarbo, was a spire point bullet like a traditional rifle.
It was met with a blank stare, like they didn’t understand the statement, and a couple of them thought it was an obscenely ridiculous idea that could never work.
I still beg to differ. You cant build a performance car with tractor tech and design. You need to throw all that away, forget about it, and begin with a entirely new platform. Then it can be improved and dialed in.


Not an upgrade per se, but took a chance on a .40 M&P Promag extended

Consensus seems to be they’re solid, or they’re junk–except a bunch of reviews say they were junk until the springs were greased. Time will tell.

That said, it’s advertised for 25rds but I fit 30 in before I stopped. Also (safely) loaded it and racked the bolt and it chambered and ejected all 30. So, meets the “technically functions” test. Gonna try it properly next range trip–a few full mag dumps, drop it, etc. Would love a large capacity mag for when the Sub goes into home defense mode–or if I run any competitions with it–but definitely not giving it the same pass I do factory mags. The regular capacity Promag I got from Keltec has been fine so far though.


The regular one you get from keltec is a promag, the only issue I had/have is that my mag started flipping the round (1 per mag) but with my Smith & Wesson oe mag, I never experienced that, keltec sent me a replacement mag though, no charge with a return envelope, thanks Ericka! :grin:


@Omnivious Ericka is the best. Sent me a replacement feed ramp with some Kel Tec goodies she is awesome


This is my first post, so if this is in the wrong spot, please move to the correct location.

I purchased four parts,KEL-TEC SUB-2000 Muzzle Brake, KEL-TEC SUB-2000 Bolt Tube Cover, KEL-TEC SUB-2000 Recoilless Charging Handle, and the KEL-TEC SUB-2000 Recoil Buffer. I may post this review on all four products, as I tested them all at once.

The Kel-Tec SUB-2000 has a surprisingly atrocious recoil management issue. I have fired MP5’s on full auto, and a Scorpion on semi, and neither one came any where near as snappy or plane unpleasant to shoot. As Chris Nelson pointed out in one of his videos, the SUB 2000 is lacking in recoil management. That is an understatement. While my Scorpion is smooth and pleasant to shoot, and can shoot it all day, I was shocked, surprised and disappointed at the snappiness and teeth rattling and “distracting” lack of recoil management on the SUB 2000, and it quickly moved from a potential SUB/handgun combo category to an emergency weapon. So I started researching muzzle break/compensator for it, and this is how I found M*Carbo.

I installed all four parts listed above, and shot it side by side, comparing it to one that was unmodified. This is not a detailed review, as far as spelling out how man shots fired from which one. But I went back and forth between the two. 17 rounds of the M*Carbo modified, then 17 of the stock (unmodified). Then 3 and 3, 5 and 5 and so on. A total of 150 rounds were expended.

While the recoil was still more noticeable, in comparison to the MP5 and Scorpion, and I still would not choose it to take a sub gun class with, the MCarbo modifications made a night and day difference. They worked as advertised, and I will purchase the same parts for my second SUB 2000. The recoil got a lot more manageable, (still blows my mind that I am talking about a 9mm carbine). I thank MCarbo for innovating their product and bringing it to the market. Thank you for taking the time and effort. The muzzle break, is beautifully machined and looks great on the SUB 2000. As a matter of fact I will purchase one for my Scorpion as well. Had I not found M*Carbo both the Kel Tec SUB 2000s would be going for sale.


Hey @Bagman welcome to MCARBO Forum! Good a place as any to start, sounds like yer well into the game so far. You won’t find much argument here in feeling that MCARBO innovation and upgrades make the SUB2000 easy well worth shooting.:+1:


I too was disappointed but still loved the versatility of my s2k. I ordered the heavy bolt from Kel Tec and that helped with recoil. Then opened it up and did the full mcarbo upgrade less the trigger bar, including muzzle break, notched site, flat trigger and polished ramp. With carful shoulder placement of the (did I mention before How much I dislike the poorly designed shoulder cruncher, I did didn’t I )butt stock, it is really a fun weapon to shoot. But do the full Monty of MCarbo parts you will be glad you did. I Shot a number of tight groups Saturday. Very pleased