Quote Originally Posted by UWone77 View Post
I just installed 2 Orange Springs into my 12.5 308 SBR and a 16" 308, both Aero M5's.

Still waiting on the PD range to open so I can see if they run better. Not any issues right now, but I know the Orange Spring is recommended if you're using an AR15 length receiver extension. I'd use the 308 buffer instead of the H3 to start.
Isn't the 308 buffer the short stubby one? If so, that should only be used in the AR15 carbine length buffer tubes as those are too short for the AR10/A5 extensions. I made the mistake once of running a 308 buffer in a AR10 extension and ended up damaging the threads on the rear of the lower receiver from bcg over travel.

That said, in principle I think you are right as the .308 buffer is about the same weight as an H buffer, so I'd probably start with an H instead of the H3.