I blogged about the new AR57 earlier this year. The AR Five Seven is a one piece 5.7×28mm upper that attaches to a AR-15 lower and uses the 50 round FN P90 magazines. 57 Center posted a few photos of their new SBR suppressed submachine gun/PDW:

How cool is that!

UPDATE: After writing a three paragraphs about integrally suppressed firearms it turns out this is not integrally suppressed! The suppressor fits inside the handguard. I got this via. email from the 57 Center:

This particular AR57 PDW Upper in Full-Auto with 6″ Barrel, with 6.5″ Gemtech Suppressor, is currently being produced for a couple LE Agencies.

We currently have our 11″ Pistol/SBR Upper available as well as our standard 16.125″

So they are now directly competing with the full-auto FN P90. Personally, if I had a choice between this and the P90 I would go with the AR platform.

I think the pistol configuration could be a lot of fun.

UPDATE: I asked if the 6″ barrel gave adequate performance. From 57 Center:

We have excellent results with both 6″ and 11″ Pistol/SBR Barrels, this would be peoples choice, LE prefers 6″ with the 6.5″ Suppressor, this unit also works in Sub Sonic,

It is very impressive that the action can cycle subsonic rounds (a light 30-50 grain 5.7mm bullet traveling below the speed of round is comparable to a 40 grain .22 LR Standard subsonic round).