Per Dr. Gary Roberts, a ballistics expert on tacticalforums.com (I wish I knew how to do the link thing right), the HST round fails in penetration of 4 layers of denim testing, a standard in testing. Now, this is for le application (the denim testing), but if you plan it as a defensive round, it would apply to you also.
Additionally, he recommends Federal Tactical as a better round, the Hydra Shok being an outdated round, not as good as other newer rounds.
If one is interested, go to the forum above, go to the terminal effects forum. Once there, click on search at the top and type in service caliber pistol. You will see extensive ballistic testing results of numerous calibers. Also recommendations at to ammo.
FYI, I have no financial interest in that forum, I only mention the forum to direct others that might be interested in expert technical info. I was referred to it by another leo on a le forum I belong to. I have found it very informative.
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