Hello. At 25 yards, older HPs would usually drop 5 rounds into about 3" or so at 25 yards with most ammunition. With loads they "like", a bit better.
Starting with the MkII HPs and continuing on, I've noted tighter bbl-to-slide fit and have also noted tighter groups, particularly with
loads the gun "likes."
In an article in "Handloader" some years ago, a fellow wanted to get a HP to "shoot" only by load developement and got groups in the 1" range at 25 yards. I don't remember the load, but the bullet was a Sierra 115 gr JHP over PB powder.