I really don't understand this, you are saying that a bullet isn't expanding. The bullet isn't designed to expand, its a match bullet. They will still kill critters but that isn't their purpose.
has anyone mentioned using a bullet designed for game and not targets? anyway, I use a 110 or 120gr ttsx in my 308 ar and 300BO. the bullet gets good velocity out of short barrels and kills very effectively. those light barnes coppers are made for the lower speed that the blackout generates, so they work good for the range you're dealing with.