Anyone who ventures into "hand-loading" usually starts by wanting to save money and to re-use scavenged brass - but variations can start when faced with shortages of your original preferred components.
When you can't buy any more xxx powder - you are forced to look around and try yyy eh.. and who knows - it might even turn-out to be better, cleaner shooting with less smoke - or it might mean you use a few grains less propellant in each cylinder full without reducing the velocity.
"While there's lead in the air - there's hope." ..
- Way back in the early nineties I was having great fun (but little success) shooting bowling pin matches with a 9mm Glock - as my standard hard-cast pills just weren't very good at slamming those pins off the tables - they were no way as effective as the fat, soft & slow .45" slugs.
Sure, I had plenty of rounds to drill through and splinter the pins - and then spin them around on the table as the bullets flew-on down range - but the oppositions heavier lead seemed to thud into the pins and stay in them - and their pins when cleanly hit flew back right off the table.
I needed something low-velocity, with soft & heavy lead for a 9mm ... jacketed for that Glock polygonal rifling - what to do?
Those slow-slung 357" pills would enter the pins and not exit - raising lumps under their plastic jackets - I won a club match & an engraved beer glass with that reduced low-speed load.
Note: There are some valuable safety remarks in the comments at the bottom of this post.
'Down-load' a 9mm to match a .45"s performance - and you've got very much the same load that I still use for hush puppy loads at around 800ft/sec. in my silenced 'Just Right Carbine'.
The way I'm thinking says that you need length inside a cartridge case to fit funny stuff into. A short fat forty-five is fine as far as it goes - but you can't shove multiples ** down it's maw. Perfection comes shaped like a stretched magnum style case.. and the latest I've found is the 327 Federal Magnum.
38 Spec. 327 Federal Magnum 357 Mag.
- Look At The Length Of That !
Now - consider that the SAAMI safe maximum pressure rating for the 327 cartridge is set at 45,000 p.s,i. and you have a strong & broadly tolerant brass case for experimental loading eh. - I'm thinking about two pills stacked 'back-to-back' or three round balls or 'one-plus-two' or ...
** A true .45"acp fanatic might maybe consider trying split multiples that look like a 'pie chart' - but they would likely fly off waywardly under the centrifugal spin?