Ar-9 Pistol Barrel Length

[GunSmoke]

I'm considering switching from a 16-inch ar9 upper, and building a pistol that I can later SBR. I'm interested to hear what you all feel is the optimum barrel length for such a pistol. My plan is to run this both suppressed and unsuppressed.

Thank you all in advance for sharing your experiences. Happy Monday.

[AshAZ]

I run a 5.5” ar9 and it’s great suppressed and unsuppressed. For suppressor use, you don’t want too much muzzle velocity or overall length so a short barrel is nice. With a suppressor it ends up being close to a 10.5” 5.56 sbr length.

[GunSmoke]

Thank you, I appreciate the insight. Do you run your suppressor under the handguard? I've seen several people do that, but I would be concerned about running it without the suppressor in that type of configuration. Muscle memory tends to cause you to put your hand or you shouldn't.

[DRTDIVR]

I've been doing lots of research on this to. Seems the consensus is +/-5" is ideal for keeping it subsonic with 124gr+ ammo when running a suppressor. Seems 8" barrel is better for a little more velocity but not as good suppressed in regards to noise and overall length with a suppressor attached. Reports don't show a big enough increase in velocity to go much longer than 5". I am thinking about picking up a CMMG Banshee soon so I've been reading up on it a lot. Banshee seems like a perfect PDW and suppressor host.

[Viper 1-26 INF]

I went 5.5" on mine as well.

[GunSmoke]

Next question is Colt patern magazines or Glock? I currently have a Colt pattern upper in 16 in that works fantastically. Any experience with the glock versions?

[superdrag67]

I have a 5" AR9 that is on a glock lower. I went glock because I already had a bunch of mags. Works great, low recoil and no hiccups so far. I wouldn't advise running a suppressor under the handguard if you are going to shoot without a suppressor some of the time. I don't think 9mm would generate enough pressure but people have split handguards running .223 brakes under handguards. Hand placement would be the biggest concern, like you said.

I'm not sure about the colt mag versions but you'll need to get an upper or lower that has LRBHO built into it if you want that feature.