AR Five Seven: 5.7x28mm AR Upper

Steve Johnson
by Steve Johnson

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 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 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 . 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

Steve Johnson
Steve Johnson

I founded TFB in 2007 and over 10 years worked tirelessly, with the help of my team, to build it up into the largest gun blog online. I retired as Editor in Chief in 2017. During my decade at TFB I was fortunate to work with the most amazing talented writers and genuinely good people!

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3 of 22 comments
  • AR Guy AR Guy on Aug 18, 2012

    I believe the reasoning for the 5.7 was to be better at penetrating body armor than the 5.56. Why would anyone who already has AR-15's need this? Because it is WAY cool!!! What lower is recommended, if any.

  • William Pope William Pope on Oct 10, 2012

    This is by far not only the most fun upper that I have for my AR's, but it is also practical. With magnifcation 200-300 yards is perfectly attainable. I shoot within 200 most of the time and can shoot 2MOA+ a little on a bench. The only issue I ever had was with a custom trigger (that I installed - there probably being the issue), and it fired just like a select fire firearm. Loved those few minutes of illegality. Got the trigger cleaned and reinstalled and I had no issues.

    need to reload because of the cost of ammo, but that is with all ammo now. Personal defense - ideal, maitains a perfect zero on target because of almost no recoil. Perfect for animal control up to the size of a coyote. Not a deer gun, but what a dear set up. Love it.

    • Bob Bell Bob Bell on Nov 27, 2012

      @William Pope I was wandering if you know of a 5.7x28 upper that would work on a DPMS LR-308 lower and if you are the infamous Willie P. from Vicksburg, MS I know from Church? If so let's go shoot sometime. BB