Let's borrow some images from Brassfetcher, showing the terminal performance of representative 5.45x39 and 6.8SPC rounds in bare ballistic gel. You can find the actual pics and accompanying text at
http://www.brassfetcher.com/AK-74 .html . Per the Brassfetcher FAQ, we can link these pics here and embed them in the discussion:
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I am not an expert in terminal performance analysis, and the comments to the pictures are solely my observations.
First up, let's look at the performance of standard com-bloc steel insert 5.45x39 53gr milsurp:
The shot direction is left-to-right. Note that the bullet yawed, but exhibited zero deformation or fragmentation. The only wounding being done here is by the intact projectile itself as it yaws. Unlike 5.56 NATO M193 or M855, there is no fragmentation that would increase the wounding potential of the bullet. Bullet yaw appears to start at 2.5" of penetration and the bullet appears to assume base-first travel at 9.5" or so.
Next up is Wolf 60gr HP, with the shot direction right-to-left:
Notice the REALLY, really long neck in the wound track before it starts to yaw. Again, fragmentation was minimal until the end of the wound track. Surprisingly, the bullet did not begin to yaw until it had penetrated ten inches of gel and the wound cavity didn't get interesting (presumably due to moderate fragmentation) until thirteen inches in. This round may be useful for barrier penetration, but it's not particularly suited for social work. This is not advertised as high-penetration ammo, and as best I know does not actually have a penetrator insert. I paid for Brassfetcher to conduct this test because I wanted to determine if the Wolf commercial offerings were suitable replacements even for the milsurp ammo, should the milsurp become unavailable. My conclusion was that I would never use Wolf 60gr HP for serious social work.
Finally - this is a 6.8SPC controlled-expansion load made by Silver State Armory, using a 110gr Barnes TSX bullet:
The wound cavity initiates almost immediately, and the cavity characteristics are quite dramatic. Penetration is moderately deeper than the tested 5.45x39 rounds, and yet the wound cavity is much larger.
All cost aside - which would you choose for HD purposes?