This comes under the Teenager* heading, but pertains to heavy load development in the 9mm.
Wayyyyy back in about 1984 -1986, when oil crashed from 20-something a barrel to 14 dollars, and Alaska could not pay its bills, people were locking the front door and leaving the state. They left their dogs to roam, and since my golden-retriever/husky -half tinkerbell mix was on a 50-yard run, he and his food dish were often the target of these abandoned animals. So one day Dad comes to the basement loading room and quietly announces (low voice for effect), "I am looking for a load for my quiet gun."
Hmmmm. The WW2 - vintage MK 2 STEN, suppressed, had the recited history of employment with the British Frog Teams in the south Pacific. That was Dad's new dogcatcher, since neighbors cut the tripcord to the SPCA-approved cage trap Dad had built the year previous. Three dogs went to the pound, at a fine of $75.00 for vet and license fees to retrieve them. So, we tried humane, and the danger remained. While he was gone on business, could I work up a kitchen-door load for these mongrel animals so as not to bother the neighbors?
Using 1950s - vintage Lyman manuals, and the molds on hand, I began with #358439, cast soft to expand, and sized to .358. I recall weight at 175 grains. Since this was a 9mm load, I used charge data for that caliber. A maximum Bullseye charge of 4.8 grains was reduced by ten percent for that vital safety margin, with the seating in a belled and chamfered case to about half way up the front driving band. It all made sense to a 14-year old.*
My ears ringing, I immediately recalled somewhat stout recoil from the STEN. I also employed deliberate effort to both remove the case body from the chamber, and retrieve the head separately. That wasn't supposed to happen. At the end, I discovered 2.5 grains of Bullseye would cycle the action, or preferably 2.7 grains preset from Dad's Star reloading machine. The big issue became feeding. The vintage Pacific die used a RN seating plug, which crushed the HP on that old #358439. I only got one out of every three rounds to escape that die in shape to feed reliably from the magazine. But it was quiet.
Ten years later, Dad's Class 3 collection all went down the road.
*General disclaimer