AR9 Barrel Length Recommendation

[WestDesertPRS]

I'm looking to build an AR9 pistol using an FM9 upper and I'm tossed up between 8.5" and 10.5" barrel length. I don't plan to suppress now, but may in the future. Will the 147gr loads stay subsonic even out of the 10.5" barrel? What are the advantages to longer barrel (10.5?) in a pistol caliber? I know a lot of people are running really short (5") barrels on these but I think I want something a bit longer.

 

[slothlacrosse]

Most people run shorter barrels because OTS 9x19 is optimized for pistol barrel lengths.

Why bother with subsonic ammo if you’re not using a suppressor?

And depending on the load, subsonic ammo might be slower out of a longer barrel.

 

[mr45acp2u]

Ballistics by the inch. http://www.ballisticsbytheinch.com/9luger.html I was looking for compact, not max velocity, i went 8.5. Looking at the chart, no hard fast rules for velocity and length.

 

[WestDesertPRS]

Most people run shorter barrels because OTS 9x19 is optimized for pistol barrel lengths.

Why bother with subsonic ammo if you’re not using a suppressor?

And depending on the load, subsonic ammo might be slower out of a longer barrel.

Sorry...should have clarified...I was asking whether or not the 147gr loads would be subsonic from a 10.5" barrel if I end up suppressing it down the road. Right now I just plan to shoot cheapo 115gr stuff.