From my own faulty memory, the Bren 10 was the brainchild of Col. Jeff Cooper and a couple of associates back in the mid 80s. It was a ballistic success but a commercial failure because the pistol it was designed for couldn't be produced quickly enough to meet demand. Plus recoil was pretty stout, leading to the downloaded version now known as .40S&W.
Warning: I know Judo. If you force me to prove it I'll shoot you.
NRA Benefactor 2004 USAF RET 1971-95
I've never seen one... but that don't mean much.
Looking for Ideal mold 419181 (44 Evans Long)
"Joined Dates" are deceiving if you factor-in "lurk" dates.
IIRC, the original 10mm ammo was produced by Norma. I don't know if the cases were headstamped Norma or Bren 10.
From one of my favorite youtube channels, a look at the Bren Ten and some history behind it.
https://www.youtube.com/watch?v=A3amzB_hVUw
BP | Bronze Point | IMR | Improved Military Rifle | PTD | Pointed |
BR | Bench Rest | M | Magnum | RN | Round Nose |
BT | Boat Tail | PL | Power-Lokt | SP | Soft Point |
C | Compressed Charge | PR | Primer | SPCL | Soft Point "Core-Lokt" |
HP | Hollow Point | PSPCL | Pointed Soft Point "Core Lokt" | C.O.L. | Cartridge Overall Length |
PSP | Pointed Soft Point | Spz | Spitzer Point | SBT | Spitzer Boat Tail |
LRN | Lead Round Nose | LWC | Lead Wad Cutter | LSWC | Lead Semi Wad Cutter |
GC | Gas Check |