The 9mm cartridge and its bolt was designed to cycle with blowback recoil, not gas. Some produce more pressure and require more dwell time to avoid over-pressurizing the receiver. Some rounds and barrel lengths produce less pressure. This is also why AR-15s have different gas system lengths. This is called dwell time, and it's why gas must travel down the barrel and through a gas tube before coming back into the receiver. But all that round's energy would 1.) quickly destroy the bolt and trigger group, or 2.) not cycle the bolt completely in a blowback-operated AR-15. That gas must expend more of its energy on the bullet itself before being harnessed to cycle the bolt. This is the only way to achieve the right amount of velocity a rifle round requires. It produces a lot of gas when fired, and burning all that powder takes time.
![ar9 ejector ar9 ejector](https://www.80lowerjig.com/product_images/uploaded_images/ar9-stripped-lower.jpg)
There’s a lot of discussion – and some confusion – about how these two guns work. The AR9 and AR-15 look alike, but each uses different parts and systems to operate. Since the AR9 pistol and AR-15 appear so similar, let’s compare the two first. A 9mm-specific buffer is required inside your buffer tube, but we'll touch on that later. Converted 5.56/.223 guns use special parts to adapt the factory upper and lower receivers for the 9mm cartridge. The AR9 pistol instead uses a new lower receiver (aptly called theĪR9 lower) and a stripped AR-15 upper receiver with a 9mm barrel, new bolt carrier group, and an AR-15 buffer system and lower parts kit. But this particular 9mm weapon is not just an AR-15 with a 9mm Parabellum conversion kit installed. The AR9 pistol (sometimes hyphenated "AR-9") is a new 9mm variant of the AR-15. All data and recommendations in this guide were compiled from real shooters who've built and tested AR9s with different parts.Ī 9mm AR Pistol Kit (which must be paired with a 9mm AR lower) is what many shooters buy to build from scratch. Looking for answers about shouldering an AR pistol brace? We wrote a guide for that, too.
![ar9 ejector ar9 ejector](https://i.imgur.com/5rvg8Xc.jpg)
When we're through, you'll know everything you need to build the perfect AR9 pistol in a supersonic or subsonic (suppressor-friendly) configuration. This is your ultimate AR9 pistol guide! We’re breaking downĮverything you need to know to build one yourself: What the AR9 pistol is, what separates it from an AR-15, parts compatibility, 9mm Parabellum's ballistics, buffer weight, barrel length, twist rate, and magazines.