T91 AR Piston upper

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    T91 AR Piston upper

    Just picked this upper up on another board. Was only looking for a set of hand guards for my A2 and...

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    To me it feels more natural in my hands that the A2. The round hand guards and the carry handle sight on the A2 never really worked for me. The TY91 hand guards are tapered and shaped more like a FAL. Points well and I appear to be getting a better sight picture while maintaining a good cheek weld. We will see once I get to the range.

    I was worried that as a piston driven upper it might be heavier but even though it is a 16" barrel and my A2 a 14.5" (heavy barrel) it is six ounces lighter. Only thing that is a slight detriment is the sight radius on the T91 is 14" and the A2 is 16.75. It came with a UTG rear sight that the PO put on it. But once I shoot it I may try something else.

    Does anyone make a folding rear sight that sits further to the rear over the area not milled for Picatinny slots?

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    Interesting but pretty simple short stroke piston set up. Used by the Taiwanese military for a long time. Here is the military version which as a few subtle differences like a FSB with bayonet lug and a more angular pistol grip. They use a 14.5 barrel in conjunction with the bayo. Some people are going all out rebuilding theirs into military configuration. I am going to avoid scratching that itch. Especially right now as most of the parts are out of stock due to panic buying.

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    Last edited by Johann; 07-12-2020, 12:34 PM.

    I know it's not folding so doesn't fit your criteria at all but I bet a Scalarworks peak rear would look awesome on that.

    I've always liked the T91 wouldn't mind putting one together



      I do like the way that looks on the firearm and it does extend the sight radius to the rear of the upper. $150...ouch!

      Honesty need to reconsider whether it needs to flip or not. Front sight is fixed but removable. Unless I upgrade to optics they can both stay mounted. The cheapo BSA red dot I have sits too low to cowitness. I could put it on a riser but might be time for a decent one.
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        Well, Hyde. You just cost me some money on ARF com.

        There were some NIB Scalarworks sights there. Full set for slightly cheaper than new. Rear alone was sold out at Scalarworks. Just about every decent sight was sold out on Midway too. So I jumped on them.


          Good choice! The fit and finish on them is incredible!


            Got the Scalarworks sights in last night, after the USPS delivered it to the wrong house... Glad they found it.

            Nicely made. Has to slide on to the rail from the charging handle side. The bolt cross pins through the rear Pic slot. It is not going any where.

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            Sets the Sight radius back about 1.125. over the slotless shelf behind the pic slots. So now just over 15. Just where I was looking to put it. Plenty of room in front for an optic mount if I go that way with this one.

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            Here is a pic looking down the barrel. I like it even better now. It has a very central balance point with a loaded mag inserted. Just under 7Lbs total. Thanks for the suggestion Hyde!

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            Now I will be figuring out a light mount off the right side of the handguard near the front sight. There is a stock tri rail available ($65!) but I only need one location so am going to experiment with some thick aluminum plate I have. There are two nutserts imbedded in the top of the handguard for the stock mount. I will see if I can home brew something simple and specific to my needs.


              Originally posted by Johann View Post

              Thanks for the suggestion Hyde!
              Didn't see the update right away but glad it worked out!

              I want a t91 upper even more now


                No sweat! Still haven't gotten to shoot it. My buddy with the range membership and I are waiting for a break in the heat.

                Had the piston out the other day and took a pic. It is an interesting self contained unit. Comes out with no tools, which is nice.

                Kind of similar to a FAL as it comes out the front of the gas block but unitized with the springs in a tube. Perhaps designed this way to work with minimally modified AR uppers. The front of the upper is milled to hold a non standard rear hand guard retainer that is riveted to the upper. The Barrel nut is different as well since it has to accommodate the piston.