"Of course it's going to be a fail."
The DPX did not "fail." If you read the detailed article, it makes sense. The anatomical illustration and discussion demonstrate that the bullet will often hit bone. Further, your point about putting something in front of the ballistic gelatin makes no sense. It is done by FBI and others as there are barriers externally as well as internally. Brassfetcher does all the above, bare, cloth, bone "simulant." Makes sense to me. Some, FBI included , I believe, add drywall, sheet metal, glass, and plywood. Regardless, the vaunted 135 +P Gold Dot leaves much to be desired in my opinion, as even in bare gelatin it fails minimum penetration standards. It failed with denim barrier in the link above. So like a broken record, I say use the Corbon DPX 110 +P if you want expansion in a short barrel .38 Special. In testing it stands above all others. As for me, I'll take some hard cast lead and a meplat and two feet of penetration from a standard pressure .38 Special.