This is my first foray into the AR9 world but I have aspirations of building a short, compact pistol/SBR.  To that end, I’ve purchased a 5.5” barrel and I’m now looking at my option on the back end.  If it’ll all work together I want to get a Law folder and a LWRCI UCIW Stock Kit.  I’ve already read about removing the weight from the rear of the BCG so the Law spacer will work.

Anybody have this setup or have knowledge of it’ll work or not?

I don't have an unmodified UCIW extension to test, but I cut down a pistol buffer tube to 6.25" internal length to use with a Nordic Glock lower, Taccom PCC adjustable buffer system, and Taccom short throw bolt.

Attached File


Blowback 9mm ARs don't need the same bolt travel as an 5.56 AR, and if you're using Glock mags you can have an even shorter bolt travel than when using Colt mags, when using a short throw bolt. If I had to guess, I'd say your setup should work fine and you may be able to substitute the LWRC UCIW short buffer with a standard carbine length buffer.

the rear of your bolt carrier needs to be able to fit an extension to make up the length difference the LAW folder adds in front of the buffertube...the double "O" ringed plug from the 5.56 kit needs to be able to work in your 9mm bolt carrier, or drill the carrier and make your own extension... although the length of travel needed for a 9mm cartridge to clear the chamber is less than a 5.56, you might want to use as much length of travel as possible to reduce bolt speed, a blow back 9mm has a lot more recoil than a 5.56 and you will need to really work with recoil spring rates if you significantly shorten the buffer tube...

at one time,I had planned on a proof of concept compact folding 7" 9mm with my LAW folder and spare 9mm lower... I envisioned drilling one of my extra 9mm bolts to take the LAW plug extension.... at the time I had been shooting 9mm PCC for USPSA for several years, and at that time  had seen a variety of problems in the early 9mm PCC platforms, and other than a proof of concept did not think it had the reliability for a dedicated defensive firearm... instead, I built a couple of G17.3 with Venom and RMR2 dot scopes, and installed them in Recover Tactical folding chassis with spare mag front ends... much cheaper as the donor pistols were in the safe and a much smaller and more reliable platform, and provided basically the same ballistics as a short 9mm carbine... YMMV

regards Les L747

Well, I guess I’ll find out and report back when I know.  I’ve got the folder and UCIW on the way.

You might find this helpful for your build:



https://www.kakindustry.com/kak-heavy-bolt-carrier-extension

For anybody wondering, IT WORKS!