It's called "Mexican Match".
We (The Alaska NG Marksmanship Unit) did this to M118, pulling the 174 grn military bullets and stuffing in 168 SMKs and 180 SMKs.
I still have several thousand 174s I load for short range and off hand practice in my Vintage Military Rifles.
CPT USAR Ret
USAMU Sniper School Oct '78
Distinguished Rifle Badge 1071