M*CARBO Brotherhood

Home Brew SUB2000 Project

I made a joke in the 80% Build Thread, which got me to thinking. Why not do it.
Then I got to thinking about the parts I have and all the mods and projects I’ve started.
I’ve decided to combine them all into this build and not have to keep up with multiple threads.
Gun-Kote, Buttstock Adapter, and Full Length Forend projects will be updated here.

I’ll be using the leftover parts I replaced with all the KelTec and MCarbo upgrades.
Basically, I only need to buy the tube, firing pin, barrel, barrel nut, etc. from Kel-Tec .
I haven’t made a list of all parts needed yet, or created a budget for this project.
But it’s gonna be cheap. As cheap as I can possibly build it. No upgrades.


Haha! As soon as I saw that comment, my first thought was ‘he’s goin’ do it!’ And you did! Or are!!

Cool! But doesn’t sound 80% build anymore. More like 97%er now👍



JB, I was just going to let him ‘have at it…’ I was looking for a good source for a lower assembly! 80% Arms is an expensive (forever) jig kit, even using the AR9 Platform ‘stand alone.’ One would be much better off buying the multi jig kit… When building 22 receivers, you have to worry if the receiver’s manufactures an industry standard receiver so that all pin holes align. There is definitely a lot of research needed when building!

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Kinda defeats the whole purpose of an 80% build if you’re going to buy a serialized tube (receiver) that’s going to have a paper trail on it.


my last couple of AR series firearms have started that way. ya know, ya pick up a spare lower parts kit , for repair parts. then you do a swap and pick up a 80% lower still in the white.
then ya get bored one weekend, and finish cut it, and figure what the hey, I will assemble it, spare complete lower and all that.

then ya happen across a stripped BC.

do I need to keep going here?

last gun show, I picked up another lower parts kit for spares, and Im already eyeing one of 3 poly 80% lowers i have sitting on the shelf…

my issue is I cannot seem to keep spare parts as spare parts… :smiling_imp:


This won’t be a 80% build. Just a build from spare parts.
It was the 80% thread that got me thinking about it.
If Chris had the 80% tubes ready, I’d be all over it.


I got that from the very first post. LOL


Is there a difference between a Gen 1 and Gen 2 bolt tube?

The only bolt tube listed on the parts page is Gen 1 only.

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dont quote me on it but probably because the gen 2 is still in production and the Gen 1 is not. I know a lot of the parts are not compatible thruout the PCC.
from the standpoint of a "outside Machinists " do it the simple and cheaper way. find a length of the correct wall thickness DOM tubing, in 1098 or 5061, take your gen 2 apart, and lay out the cuts necessary on the blank tubing.:+1::+1::+1::+1:


Big difference I know is that the G2 bolt tube is the serialized part. The G1 bolt tube is not.

It is an interesting question 'cause if they are swappable folks could deface a serial number by installing a brand new part. For this reason, I would expect that they are not swappable.


ATF musta changed something around again, in the 90s, AA arms out of mint hill was slapping out copies of a tec 9,(machine pistol craze days) AP-9. THEY stamped the serial on the bolt tube, as the bolt/tube/barrel are 1 piece, and the grip frame trigger assy are the second piece. they ran into issues with bad poly, frames/receivers started cracking at the magazine catch. at that time ATF in all its wisdom, decided it could not be stamped on the steel bolt tube assy it had to be stamped into the plastic receiver/frame. That put AA arms out of business, as they were going to have to replace all of the AP9 s out there with new firearms. (new bolt tube and frame) I know a machinists up in NC that is stuck with 8,000 plastic receivers, serialized, that he can only sell with full ATF paperwork on each… Paper work trail on the one i own is longer than a johnny cash Cadillac.I bought 3 receiver/frames before i found a good one, that one gun is listed as 5 guns, so i had to save the cracked plastic POS frames.


I sent a request to KT for info on buying a new barrel.
It’s been nearly a week and no reply from them.
Next step is to call and try to get the info.

I’ve created an item list of everything else I’ll need.
Price comes to $130 before tax and shipping.
That’s calculated with the cost of the Gen 1 tube.
I’ll have to inquire about the Gen 2, when I call.


Things needed that are not listed on KT parts page:

Hinge S2K-102
Bolt Head S2K-151-9
Bolt Tube S2K-246
Barrel S2K-100-9

The bolt tube (receiver) looks to be an exchange item only.
So that will likely kill the whole project, but I still gotta try it.
I should know all I need to know after the phone call Monday.


I don’t think Kel-Tec checks there messages but twice a year I’ve sent them numerous messages and get replies on one out of three I send not very good odds :man_shrugging:t2:

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Haven’t forgotten about this or given up, just been so busy at work lately.
I’ve been pondering some changes to the stock adapter and forend.
But again, haven’t had time to put anything down on paper, so to speak.

I think Chris will have to release an 80% tube for the rest of this project to go farther.
Getting a receiver from KT is probably not gonna happen. Hinge and barrel, maybe.

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