I did some shooting into Clear Ballistics gel with the FBI .38 Special service loads, and a similar cast bullet handload. Chronograph results are of the actual fired projectiles. Test firearm Ruger Police Service-Six .38 Special stainless revolver with 4" barrel (catalogue GF-84). Temperature 70 F.
The Remington ammunition is about 30 years old, the Federal and Winchester about 25 years old. Stored in controlled conditions.
The handload is about 5 years old, using the Rimrock SWCHP gas-checked cast bullet at a claimed BHN 5. The HS-6 charge is 1/10 grain above the starting charge for a jacketed bullet in the Speer Atomic Manual (Number 8). Primer is Federal 200M.
I have an equivalent jacketed bullet handload, but since this is the Cast Boolits forum, I left it out of the picture, so as not to set off too many members...
Results pictured.