11.5” or ? What’s the “sweet spot” for a smooth running pistol sized AR?

Looking at an upper for a compactish truck gun.

https://www.aeroprecisionusa.com/m4...e-upper-receiver-w-atlas-s-one-handguard

https://bravocompanyusa.com/12-5-carbine-upper-group/

Yes, 11.5 is generally considered the sweet spot.

7.5" 300blk

In 5.56, I have a DD Mark 18 10.3”.It has been reliable suppressed unsuppressed. That’s the shortest I’ve ever experienced a 5.56. 300 blackout I have a Sig rattler 5.5 inch barrel with roughly 700 rounds down the tube suppressedSo far so good. I have only run Gemtech 180 grain subsonic.