Hi,

I know the question at large as to whether or not bufferless AR 9mm pistol systems have been designed before has been asked. That's not what this forum thread post is about.

I am looking to build an AR upper (compatible, but not necessarily uniquely designed for 9mm) with side-charging capability and bufferless technology. I'm not looking for stuff like this (DFA Buffers), but more so trying to build something like this (which was previously posted for distributors' pre-orders on this forum last summer), except using standard, non-proprietary components as much as I can.

Upon closer inspection, most such bufferless AR pistol variants have been designed with either a short-stroke gas piston system (for rifle calibers) or transformation of a standard buffer recoil spring into a thin, long one that can fit in the gas port of a forged upper (for pistol calibers). Can I buy such a stripped upper and start building? Could I modify an existing upper receiver to handle this?

Really interested in removing the prodding stick of an AR in a pistol variant. Many so-called 'micro' buffer systems really are nothing more than a glorified 1/3 buffer tube (by length). Really doesn't feel even remotely close to real 'bufferless'.


Thanks!

So what you are saying is you want an MPX


Or  K-USA kp-9

It would be a hell of a lot cheaper and easier to just buy a CZ Scorpion EVO.

Building a side charging bufferless AR9 from scratch can be done, but it's kind of like trying to fit a square peg in a round hole.  You're going to end up spending way more time and money and frustration than it's worth.

If you're dead set on doing an AR9, I would wait for something like this to come back in stock:
https://www.rainierarms.com/r-d-precision-9mm-gen-2-pw9-bufferless-upper-kit/

So part of the problem you are gonna face is bolt length and weight.  With pure blowback, you depend on the mass of the bolt to help hold things closed.  With a 9mm AR bolt, if you shorten it you start loosing weight from the heaviest spot on it.  You need some way to replace the weight or compensate for it being gone (ie something else besides bolt mass to keep chamber from unlocking too soon).

The next part of the problem is the spring, either used to completely stop and control that bolt from slamming into the back end at speed (at least slow it down a good bit) but also to bring the bolt back forward with enough energy to easily strip a round off the mag and chamber it and close up tight.

For the second part, running a rod where the gas tube would normally be and having it attached to the bolt/carrier where the gas key would be, with a heavy spring on the other side that is compressed as the chamber opens might work (think AK or Galil piston system style).  Or a spring on each side with just a rod in the middle, something like a T handle on it push a spring on each side.  

All FALs use two springs - one up front to return the piston, and one in back to slow and return the bolt.  The para model still has the front spring set up, but the rear spring is changed from the rat tail pushing on the spring in the stock to a pair of much smaller springs that run in the upper above the bolt carrier.

So that one was the one I already knew about, linked in the OP.


@eyegor, would it be possible to just get a BRN-180-like upper that's chambered for 9mm? Or is there no AR-180 9mm upper that is compatible with std. mil-spec AR-15 lowers?

Perhaps.  But you have to remember that the 180 (and FAL and AK and all those others that have true folding stocks w/o buffer tubes etc) has something going for it a 9mm PCC typically doesn't - a locking system other than pure blowback.