I posted the same question...

for my dad mostly, he's shot 2-3 deer with them, rather close range, probably 50yds, and agreed, hit them well, but they just seemed to fragment.

He shot a doe a while back with barness expanders at 100yds, it fell over dead. All of his SST deer stood there like they weren't hit, all were found/killed, but kinda annoying to shoot a deer and have it just stand there looking at you, even if its dead and doesn't know it. His 1 buck he put 4-6 shots in it with those SST-s, 3 of them were in like a 2" circle near the deer's heart, how that buck stayed moving, alive for so long...

That particular deer, took I think 3 shots, eventually laid down, then got back up...

I'm pretty certain he's done with the SST's no matter how well they shoot out his slug.

I wonder if they're too light/fast? but they're not any lighter than a rifle bullet nor faster, just not sure...

But he's going back to those barnes expanders probably.