Anyone running a 7in barrel on their ar15?

[Medic650]

I just want to confirm my understanding on these threads. 300 whisper with gas block in pistol position will not cycle reliably without the can with barrel lengths in the 8-8.5 inch range? I was thinking of shortening my 12 inch barrel down to reduce overall length. I do have a PRI adjustable gas block so maybe I could open up my gas port more for unsuppressed. I rarely shoot it without the can though.