Without prior ATF approval, that is.

This pretty much happened because I had a couple spare A2 grips and a front sight with no home.

The conceptual rendering:
Screen Shot 2016-04-21 at 6.33.40 PM (1) by Slick_Rick77, on Flickr

The real deal:
20171013_081213 by Slick_Rick77, on Flickr

20171013_081144 (1) by Slick_Rick77, on Flickr

This was originally one of those hideous UTG sights. It looks pretty good with the back cut off.

20171013_082314 by Slick_Rick77, on Flickr

A2 VFG. Because.
20171013_081301(1) by Slick_Rick77, on Flickr

This cut down A2 grip was a temporary fixture on another build. This is a permanent home.
20171013_081251 by Slick_Rick77, on Flickr

I've been without a pistol caliber carbine for some time, didn't have anything with M4 furniture, and had nothing with removable fixed sights front and rear. This is all those things and gets rid of some spare parts that would otherwise languish in a box forever.

Its primary purpose will be a quieter indoor range gun that's a little less expensive to shoot. I may form one a suppressor for it. Not entirely sure on that, yet.

It's a 10" barrel, 28-3/4" overall, and 25-1/2" collapsed, mostly comprised of RRA and Anderson Mfg. parts.

Have you thought of throwing some CAR slim handguards on it to see what it looks like?  I generally like CAR more than M4 for plain jane handguards.

Yeah. With that high FSB it looks terrible.

I did a 10.5" and used a YHM flip up front sight that's made to clamp over a shaved FSB. It looks pretty good IMO

I don't use it much since I built a another upper with a 5" Tros 3 lug barrel

Looks good!  9mm SBR's are a lot of fun.

I was really tempted to go A2 front and A1 upper (they look awesome), but this allows it to be 1/2" shorter. It works

When boresighting it, no adjustment was necessary. That's a first.

I haven't had a pistol caliber carbine in a decade or so. I was missing it a little.

I've test fired it with some hollowpoint ammo. It's all good so far.

New front sight. Old pics gone. It is now acceptable.
20171013_081213 by Slick_Rick77, on Flickr

20171013_081144 (1) by Slick_Rick77, on Flickr

20171013_082314 by Slick_Rick77, on Flickr