I loaded 9mm cast in the 80's with a Lee 124 RN and 4.8 gr of WW231. This load was for jacketed bullets and shot better with Cast. It came from a Winchester flyer.

The funny thing about this load was, it was clean as a whistle in my 39-2, but filthy in my Star BM and BKM. I think it had to do with barrel length.

I would load this recipe for my full auto MAC-10 also. The 6" barrel was out of round (an oval .348 x .360!) I sized these 124's to .357/.358 (didn't make any difference). At 50 yards and with the silencer, 5 round bursts were about 6 to 8 inches, with just a barrel extension, the same ammo grouped 12 to 18". Even with firing from an open bolt they were very clean burning. 5 rounds was the smallest burst you could do consistently with ammo this hot! (with subsonic 130 Sierra Tournament Masters, 3 rounds was very easy to do, accuracy was in the 3.5 to 4.5" range!)

I loaded around 30,000 of the hot 124's over 20 years. Unlike foreign surplus (pre NATO) military FMJ ammo, I never had a feeding issue! This load was more like NATO ball (Winchester White Box), but much cheaper!

Ivan