I’ve had a 9mm AR for over ten years.  It gets a lot of use, especially in the cold weather months because I can shoot it at indoor ranges.  I’m a fan of 9mm ARs.  Also, in the last year I’ve gotten into AR pistols.  I have two in 5.56; now it’s time to build one in 9mm.

I’d like this to be a minimum footprint sized PDW inspired pistol with a 5.5” barrel.  Some design features have been decided, others I’m still researching.  Hopefully someday I can SBR it, but until then I’m perfectly OK with cheekwelding it.

First up is sorting out the lower.

This will definitely be on a Quarter Circle 10 Colt pattern lower which is already on order.  The entire lower is planned out except for the recoil extension.  I think I’d like to try a reduced length RE system, the footprint of kteaton’s SBR with the MVB ARC stock which is shown in the last few pages of the 9mm Gun Porn thread is very appealing.  If I don’t do that I’ll just use a RRA pistol RE with a foam cover like I did with my 7.5” 5.56 pistol.

Is anyone else doing a reduced length RE that would be usable for 9mm without modifying the BC?  I’m trying to find the IL of the ARC’s RE so I can search for similar length REs.  I remember reduced length REs were common years ago but they fell out of favor ages ago, I’m not sure if any are still in production.

Hmmm, I wonder if I should just use a LWRC UCIW receiver extension with one of Slash's 9mm buffers...

This is probably your safest bet, and it sets you up for success when you decide you want to SBR it. All the parts exist and are proven to work, and it gives you the form factor you're looking for.



Also I did see your IM and will respond shortly.



ETA: You might not find much similar in length to the ARC's buffer tube. It uses a double spring setup so its not your typical buffer/spring setup.

I think the lower specs are set - I’ll go with the LWRC UCIW unless something comes up.

Now, to the upper…

I’m thinking a Vltor MUR-1S with a TBD 5.5” barrel, a Samson Star-4 or DD Lite 4.0, a Quarter Circle 10 bolt, a Smith Vortex, a BCM Mod 5 CH and HK 416 sights will be the way to go.

EDIT: robertrtg.com has replacement drums.

I have 416 sights on my 7.5", and you're right - it would be an improvement!  I might look at doing the same for that pistol, too. I thought the drums were riveted, though?

Not on the 416 sights I bought from robertrtg.com. It came off with two screws and swapped out with ease.

I'll have to look at mine again - thanks for the lead!

It's coming together quickly - I ordered a UCIW kit (for the RE) and a Vltor MUR-1S today.  The lower is pretty much all sourced, now I need to work on the upper. I wish I could find a stainless 5.5" barrel but so far no luck. I'm also hoping to find a DD Lite 4.0 rail.

I was looking at the HK sights as well. It looks like they have the 416 sight set with out the drum, and the mp5 drum assembly separate. Is that the way you went?

Is the QC10 bolt GTG?  My only experience is with a RRA bolt which I had ramped.

Any other bolt suggestions?

(Edit) Started a new thread about the bolt

Pretty much everything is now on hand except the barrel, rail and sights.

I'm having a hard time finding 4" rail options. I'd prefer a DD Lite 4.0 but they are out of production; a Sampson STAR-4 is another option. I almost wish I could find a 4" Keymod so I could use Noveske rail covers with their integral handstop but I'm not finding anything.  An ALG would be perfect, too but 8" is the minimum there.

Before I just say screw it and order a Sampson, does anyone else have suggestions for a 4" rail?

EDIT - I see YHM does at least one 4.25" rail, the KR7. Anyone have experience with these?  I haven't used a YHM rail in many years and I wasn't impressed with them back then.

http://slrrifleworks.com/index.php?route=product/product&path=66_106_137_127&product_id=531

How about a little longer with the Odin Works 5.5 .  Below is the Odin with a TROS 3-lug and a 3-Lug Flash hider:



Also...here is a 4" Keymod:  http://www.shop.masdefense.com/GTLKM-4-KEYMOD-FREE-FLOAT-RAIL-PISTOL-GTLKMP.htm

I like that MAS one, mainly because it's cheap!  I wouldn't lose much if I find a DD Lite later. Thanks for the lead!

https://www.ar15part.com/product-p/759mmwassu1x10fsg1cl.htm

I am looking very hard at this guy for a shorty build. I have the matching carbine size upper. The Wilson barrels are very accurate the folks provide top notch customer service.

Like the plans you have made so far.