This is very interesting. A one piece 5.7x28mm modular upper that attaches to a AR-15 lower receiver and uses 50 round FN P90 magazines.

TrueWPN at AR-15.com took these photos. Click to expand.

Well this thing is interesting. Its a AR-15- PS90 cross bread. The one piece modular upper snaps onto any AR-15 lower. Allowing you to fire 5.7x28mm with the PS90 50 round mags. I added HK 416 rifle sights. I wanted to use the LaRue Tactical Aimpoint mount in the picture but I think the sight may stick out to far to mag change:( we will see. I just used a DPMS complete lower with a Magpul grip and stock. It has a right side charging handle. The upper and lower color match perfect. I am really impressed with the quality.

It still has the bolt open feature like the AR-15. It does utilize the buffer tube with the stock AR spring and a Heavy buffer that came with it. It ejects the spent cases through the mag well. I had a cheap 30 mag that was no good so I gutted it and cut the top off so it will work as a funnel for the spent cases. I purchased the Upper from www.HKSpecialist.net who shipped and I received it over night. Great guy to deal with. Unfortunately I can’t find them for sale anywhere else and I got the only one Gordon had left. The Manufacturer’s web sight is www.57center.com . I put 150 rounds down the pipe today after work with out a hitch. Really sweet accuracy at 50 yards open sights. And it was easy to engage multiple targets with no recoil throwing me off. I cant wait to put a optic on it. I am leaning towards a Aimpoint Micro T-1. Enjoy the pics…………………

The 5.56mm AR magazine is not used.

These photos are from the 57 Center’s website.

Hat Tip: Defense Tech