I think it partly depends on what performance are you looking for. I shoot a lot of pigs and deer at similar distances. My goal is always DRT. I don't want to look for game, but I'm also not concerned with losing a little bit of meat. I shoot through the shoulders and expect the shoulders to be destroyed with exit wounds.
To accomplish this, I like using short, suppressed rifles that are handy. I also like to use heavy for caliber ELD-M's. The fragmentation and wounding in combination with sufficient penetration to cross the body delivers outstanding performance. I have found that when sectional density of the projectile is high enough and velocity is maintained (goal is starting at the muzzle with 2700-2800 fps - that provides enough velocity for these ranges to deliver performance needed in my experience) that caliber of the projectile doesn't particularly matter.
So, when looking at 16" barrel, the 6.5 cm doesn't drive the 147 ELD-Ms into that velocity window. I believe a 22 cm or 6mm cm will be capable of doing so. The 16" 6.5 cm I have been using has been working well, but I am not consistently getting exits and some movement of game before expiring after solid hits. I intend to build a 16" 22 or 6mm soon to confirm performance, but haven't done so yet.