On a previous post I mentioned that I was going to spend Sunday building an AR-9 pistol.

Spike’s Tactical has a good reputation and I managed to acquire this for a decent price. I was lacking some part which I got at a gun show on Saturday and on Sunday I finished the lower without having to search for flying springs or much cussing.

The I tried to mate the KVP upper and it simply would not work. It refused to seat.

I inspected the inside and I saw that there was contact between the upper and that wire-thingie holder (Yeah technical name)

I did a silly experiment: I mated a PSA lower from a pistol I have and there was a perfect match. I even managed to shoot one round through it.

I hate complications on stuff that is supposed to be simple. I am not going to go the Way of the Dremel and suddenly I dread to go chasing another lower from another brand to see if they fit, especially after doing some reading in different forums and realizing AR9s is not an area known for its standarization.

I will be looking into some of the conversion/adapters for stardat lowers out there and a couple look promising.

In the meantime, if anybody is interested in a 9mm stripped lower, email me.


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By Miguel.GFZ

Semi-retired like Vito Corleone before the heart attack. Consiglieri to J.Kb and AWA. I lived in a Gun Control Paradise: It sucked and got people killed. I do believe that Freedom scares the political elites.

4 thoughts on “Disappointing AR9 news”
  1. I went through the exact same experience several years ago. Now I always go with the same brand for upper and lowers. But with my very first effort doing an AR rifle build I used a Brigade lower which mated perfectly with Aero Precision upper, both bought on sale.
    Have you any news as to what uppers fit the lower you have?

  2. AR pistol manufacturers play the “mating game” with components…. stupid, but typical. I bought a Quarter Circle 10 .45 AR pistol and made it an SBR. we had to dremel in a feed ramp on the chamber as it didn’t have much of one. Many of the pistols require “adjustment and fitment” before test fire. sorry you found out the hard way…

  3. That looks like a bolt hold open device. I could see where different manufacturers could implement that in different incompatible ways.

  4. Dang. Looks like you can see where it’s scraping on the upper.
    I was going to suggest seeing if you could cut a pocket out etc. for that piece to fit in and move … but then I had to wonder whether it would even work as it’s supposed to. E.g. if it is a bolt-hold-open device as Steve says, is it going to work with the upper even if it can fit?
    I presume mag commonality is a consideration? Otherwise I would suggest looking at Endomags (https://www.meanarms.com/products/detail/endomag-9mm) and a conventional lower.

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