I had Jim Milks (Innovative Custom Guns- former head of EGW Custom Shop) put together a 9mm/.38 Super after I located "parts".
Found a nice, 70 series 9mm Colt and an old, pre 70 Super slide.
Jim welded frame and lapped both slides, installed ramped, Kart barrels, blah/blah.

Here's the Super upper and a 50 yd./5 rd. target from bench.
Load is 147 Zero JHP, HS-7 (discontinued but I have a couple 8's), CCI SPP, SuperComp brass and 1.250" COAL. Velocity is 1140 FPS.





Here's the 9mm slide/upper.
Group also at 50/benched.
Load is 124 PD JHP, Titegroup, CCI SPP and 1.150" COAL. Velocity is 1030 fps.
I lengthen the leade in my 9mm barrels to shoot the longer COAL rounds.
The accuracy seems optimal and feeding from 10 rd. magazines has been flawless in 10's of thousand rds.

Both the Super and 9mm groups were <2" (barely).