M*CARBO Brotherhood

New Collar Design On SUB2000


Yes, with a new collar nut and receiver halves. I wouldn’t do it, though. The old version with the metal collar nut is more secure and I’d lose functionality with the new collar nut. I wouldn’t be able to use my MCARBO single point sling mount that slides over the metal collar nut. The new one is too big and I wouldn’t want to be clamping down on plastic instead of metal anyway.


i woke up this morning thinking about this issue. this might be a rubgoldberg approach but here goes.
I recently had too much time on my hands after being away from this forum until a couple of days ago.
I had a new trigger bar sitting by my mouse and installed it (see my posts in triggerhappy’s polishing …" thread.
The old collar nut “threads” onto the receiver. I have almost all MCARBO mods but thinking now of sling mount…
Why not just machine “crimp slots” in the old collar nut ( using the " threads" as splines) and install the sling mount doubling as a retainer sleeve?

Can the new type of a collar nut be replaced with the old style ?

By the way where is the “new things you would like to see Macarbo make” thread ?


That’s already been done.



Thanks Scott. I checked it out and will inquire to them on delivery. I see dave67 has responded the same info. Will go forward with that maybe next month.



Scott, it arrived Saturday and Wow is it secure.
If anyone ends up with a S2K that has that new nut and wants to put a QD sling mount on then this seems to be a good way to go.


@Turmeric1 Thats great, glad you like it as much as I do. I believe the PSM slotted collar nut with PSM single point sling mount clamp is the best way to improve what Kel-Tec has given us to work with on the Sub-2000. Using glue to hold a collar nut on to me is just rediculous. What you now have makes taking the Sub apart and putting it back together much easier.


I have a SaveySniper sling that already had QD’s for the Tavor. i hooked it up and bounced the S2K up and down.
tried to twist it off and feel comfy with doing so.

I just spent time modifying my trigger pull and found another benefit to this PSM collar/sling mount.
You do not have to remove anything related to the bolt because you do not have to use a wrench to break the 3M380 loose. Now when working on “inners” you have the bolt there to drop the hammer on.

this is how easy it is to get into the grip with PSM collar.
Loosen up one of the hex cap bolts and slide collar back. then remove grip side


Don’t worry Just enjoy your sub 2000 like every one else. It is so much fun to shoot.


ahy newbies that do not like the Glued collar should read this thread


I’ve got the same problem - it comes off with just one finger’s pressure now. I’m going to try the old metal collar nut and Loktite 380 unless you’ve heard of another fix. I DO NOT want to send it to Kel Tec and pay shipping for them to put another breakable plastic nut on it.


Go to the thread New Collar Design On SUB2000 and go to this link
[ http://www.performanceservicesmachining.com/kel-tec-sub-2000-products/kel-tec-sub-2000-generation-2-modified-castle-nut/

You will find something that looks like this

It eliminates the glue issue and the collar removal issue. Buy just loosening one screw you remove collar and then slip collar over rear of receiver and it is back on.
Between that and the detente MARS REENRY device and the plastic cup over detente you can take the S2K grip apart and back together with MINIMAL effort


thanks, but that looks like the split metal nut - mine is “gen 3” plastic collar. Too big to put the sling mount around, and absolutely no holding power at all. Terrible “improvement.”


Thanks, another thing to do when I open it up for cleaning this summer. I used quite a bit of glue on the collar when I finished my internal upgrades so it’s REALLY on there. Will probably have to hammer it off. LOL


Thanks for all the info - Kel Tec says the receiver halves are not the same diameter (stock metal nut won’t fit). They want me to send it back to them (I pay shipping) so they can fix it. I’m very leary of that since it is modified with all the MCarbo parts and has been cut threaded, pinned and welded with a new comp. I’ll try the metal nut before I do anything else - will let you know if it works!


I am luvin that QD sling attackment. My butt mag holder mod deleted the sling attachments on the stock and now all I have is the MCARCBO SP mount that is rotating with the silly glue on “castle” nut. I wanna take mine (early gen 2) to a bandsaw and put a couple slits in it and lock it down with a big clamp (and some black max) like the one in you pic. :+1: BTW why is your safety detent pokin’ out lol


Dave that picture was one I used while developing the MARS REENTRY device.
I just picked that picture to show the PSM castlenut/sling mount as a demo.
After I chose that picture I was wondering if someone would pickup on the fact the detente was in a wrong position.
THe nice thing about the MARS REENTRY device is that the detentepin and spring does not have to be under tension until the MARS device is applied to insert the pin thus no fear of LIFT OFF.

Your thought of the band saw is one I also considered but @Wedge turned me on to the PSM folks.
I like QD sling mounts. That way I can configure my SAVEY SNIPER SLING for many different uses.

Also the QD castlenut makes it real easy to “GOD FORBID” i would have troubles in the field with having to disassemble or WHO KNOWS me I might just want o take it apart to admire the MCARBO parts inside.
Or SHTF and I need to do a repair when the safety of my friends are in danger.


Bradley, I do not know what the extension on the rear of the receiver looks like. if you take the castle nut off take a picture and post it here. If the extension is large enough that you can file, sand or grind it to the proper exterior diameter then you might be able to fit the PSM castle nut and Sling mount. Then NO problems.

Anyone out here know if that can be done ?


Suggestion. Just cut the slits and use the Sling mount. That should allow you to use NO GLUE.
I know the rig I have is STRONG !


@Turmeric1 thats what i did with my gen 1, this go round, had it off to upgrade, milled 4each 1/16 slots in the cup, reinstalled it with the vibra-tite, and installed the MCARBO single point sling mount.

up to 350 rounds since the upgrades(i been slacking) and not a ghost of a movement yet.

I had no movement on mine originally at 1000 rnds, but i wanted to make it easier to remove for access.


I think it would be nice to see MCARBO put one out.
I think it would be an easy thing to get designed and produced.
IMO that should be an included mod on any collaborated design KT/MCARBO series.