To be fair to my LGS owner (who sold me the P365), he didn't even have any HST in stock to sell.
I went in to ask him if there's a better 45ACP carry gun than my Kimber Ultra TLE II 3" compact 45ACP, which is not all that much bigger or heavier than the Sig P365, and is quite comfortable to carry.
The LGS owner then mentioned how that very few people are carrying 45acp these days compared to 9mm, especially if loaded with modern 9mm ammo. That's when he mentioned the 9mm HST 147.
He had performed ballistic gel tests. He pulled a slug from the cash register and showed me how perfectly the bullet expands in ballistic gel. This would transfer almost all its energy into the subject and not over-penetrate things like walls.
I still like the idea of 45acp, however. And I hit with the little Kimber pretty well.
I practiced carrying the Kimber in Condition 1 (locked and cocked, but with no bullet in the chamber at first) to see if the safety came off in normal carry using a good Galco Avenger holster. The safety never moved. That, combined with the grip safety, gives me good confidence that I can carry a locked-and-cocked .45 safely -- perhaps more safely than a striker 9mm with no external safeties at all.
I realize it's an eternal question -- 9mm vs .45acp -- and the best gun is the one you're carrying, but I like that Kimber 45. I can remember admiring John Browning's 1911 design in, like, the 3rd grade (circa 1960), long before I ever even held one. When I got my first .45, it was love at first sight. I still have that gun and will never part with it.
There's lots to be said in favor of the Sig P365. It, too, is a great gun.
I just thought it would be an interesting experiment to load up a 147gr projectile to Federal HST specs.
I suppose I need to make some ballistic gel for more thorough comparison. I really don't know how well the JHP will expand at practical velocities out of a short barrel.
That's another thread, however....