Two of my rifles are candidates for getting a suppressor, a SilencerCo Omega, when tax return comes. They are:

11.25" Colt 6940 (cut down) with .073 gas port and H3 buffer

16" Colt 6720 Carbine with Spike's ST-T2 buffer (I know that those buffers aren't liked around here, but that's not part of this discussion)

Am I right to assume that the 11.25" rifle will have more gas blowback than the 16"? Is that something that needs to be tested to see if it's even an issue?
I'm considering getting an AXTS Freedom Bone charging handle to test with the suppressor, debating on getting one or two for each rifle.
Thanks guys.