I am looking to build a 9mm AR SBR with a 6 inch or so barrel (not stuck on barrel length).  I want to use a rail on it that will go over a suppressor for an overall length of 10 or 12 inches, around there, a dedicated 9mm suppressed sbr.

I will not be shooting it without the can, and if i do i will build a second upper dedicated for no can.

Does anyone know what rail is large enough to go around an octane 9?

ideally it would look something like the DD 300 SBR, that is what i am intending

my AR9mm with an Octane 45.

If you don't intend to shoot it unsuppressed, i think a specter length (~9.25") HG would look great

When i shoot mine unsuppressed i put a flash can on it and it sticks out ~1/2"

Rainier Arms/Sampson carbine length
5.25" barrel

this

I use a 5" tros, octane 9 3 lug and 9" M4e1 upper and rail from aero precision. About 1.5" sticks out end of hand guard.

Any of the m4e1 rails, seekins bar rails and spikes ones will be a large enough ID to name a few.

I used to run a ti-rant 45 inside of samson Evo, and my suppressor sits easily inside of my Seekins MCSR rail.

I run a 4.5 inch with 10 inch rail currently.  A shorter barrel like sub 5 inch helps keep most 147 gr sub sonic.

Seekins Bar