CMMG Banshee 9mm AR9 Pistol

[Balrog]

I got one of these about 2 weeks ago and finally got around to shooting it today. I have the 8 inch barrel version. I placed a Trijicon MRO red dot. It took 6 shots to have it sighted in. Then I fired about 200 rounds through it. Ammo used was Winchester 9mm NATO FMJ, Federal 124g Hydashoks, and Federal 124g HST. Magazines used were two 33 round Glock 9mm mags and two 17 round Glock 9mm mags. The only distance I shot at today was 75 feet, offhand, not supported.

Gun functioned 100%. No hiccups of any kind with any of the ammo used. Accuracy was good, with everything falling in the black circle of a 50 foot pistol target. I am very pleased with its performance.

The pistol brace is a little bit shorter than what I like on an AR carbine, but did fine and did not feel awkward.

The 8 inch barrel was very handy and makes for a lightweight, fast, maneuverable package.

The question I have is about ammo selection. 8" is longer than most 9mm pistol barrels. Is any ammo in particular more suitable for this barrel length?

 

[lsudave]

I'm just going on conjecture here, you probably get a little better velocity from the longer barrel.

If you have a chrono, I might suggest you pick up some Yavex 124 gr (I think Selway still has it). It's a Turkish brand, Turkey is a NATO member, and I strongly think it's their issued stuff, instead of a range load. It's significantly the hottest non-+P stuff I've shot, and wonder if it's in the +P range. It comes with a lacquer sealed primer, and the fireball is noticeable.

I've seen videos of people chronographing it out of a M&P (I think), and it was consistently over 1300 fps.

 

[JJE]

I'm in the process of getting my first AR9 with a 7" barrel. You can check out the ballisticsbytheinch site and see that the velocity increase going from a full-size pistol barrel (around 4") to a 7" or 8" barrel gets you a definite velocity increase, but less than 150 fps in most cases. So I would say that any defensive ammo would likely perform at least as well in the AR9 as in a conventional pistol - meaning full expansion and similar penetration. However, if you use ammo specifically designed for a short-barreled pistol (and there are a few of these on the market now that there are so many sub-compact carry guns available), it's possibly that the bullet could be over-driven and come apart rather than simply expanding. So I think that if you avoid short-barrel ammo, any defensive ammo that feeds reliably in an AR9 should give acceptable performance.

 

[zaitcev]

The question I have is about ammo selection. 8" is longer than most 9mm pistol barrels. Is any ammo in particular more suitable for this barrel length?

Chris Baker of Lucky Gunner looked into it and he suggests 147 grain HST for self-defense. His reasoning is that lighter bullets fired from carbines quickly go faster than their design assumes and then their expansion becomes uncontrollable, while they lack the energy that permits rifle bullets work even at their small diameters. But the heavier bullets for not pick up as much excess velocity and so they continue to work normally. He admits that his experiments were not exhaustive, but for that's how it is for 2018-2019 ammunition.

 

[C0untZer0]

I always was intrigued by 147gr +P rounds out of a carbine but, I've heard it posted here before that unless you have something like a roller-delayed action or a heavier-than-normal bolt, some of the energy is wasted just making the bolt go back faster and you don't get the ballistic energy gains you might think.