Question on All American Barrels

[Slapp]

I like the silencing ability of the All American barrels and am tempted to find one in .689 bore to try out. I prefer not to have the barrel be any longer than it needs to be for efficiency though and the barrel ports on the All American's extend quite a ways down the barrel length.

On the 12" All American's how long is the non-ported section of the barrel? Can anyone tell me what length of All American I would need to get in order to have about 8 to 10 inches of non-ported section on the barrel?

Thanks!