Last night I looked at my Phillip Sharpe "Complete Guide to Handloading" Mine is a 1950's edition, not the 1937 first edition!
The only powders Phillip Sharpe shows for the 38 Special are Bullseye pistol and Unique. It is my recollection that Bullseye pistol powder was commonly used by cartridge manufacturers, may have been the original smokeless powder used. Lafflin and Rand also had "Sharpshooter" , "Lightning" "W.A 30 " and "Infallible" powders. Bullseye was advertised for pistols and revolvers, "Infallible" for shotguns, the others for rifles. Sharpshooter was for reduced loads in rifles, don't know if it was used in handgun cartridges. Unique came on the market place in 1900.
It is possible that giga tons of Bullseye and Unique have been blown down the tubes of 38 Specials. I do know both powders were popular competition powders, even now a 148 LWC with 2.7 grains is a go to target load. I think the bullet has to be close to 700 fps to stay stable at 50 yards.
Colt Python Stainless Steel, 6" Barrel
148 gr LBBWC
2.7 grs Bullseye 38 SPL cases CCI500
24 Sept 1999 T = 78 ° F
Ave Vel = 710
Std Dev = 18
ES = 72.02
High = 746.1
Low = 674
Number rds = 32
I settled on 3.5 grains Bullseye pistol powder with a 158 lead (RN, LSWC, etc) and have shot tens of thousands of rounds through a wide variety of 38 Special cartridges. My velocity goal is 760 fps out of a four inch barrel, this based on early factory chronograph data. This load is accurate out to 50 yards in everything. I am confident the load is standard pressure, Sharpe's book shows some pressure tested 158 grain loads at 1000 fps! Too fast for me! I also settled on 158 grain bullets because the vast majority of my fixed sight revolvers are regulated for 158 grain bullets.
shoots to point of aim with a 158 grain bullet
shoots to point of aim
shoots to point of aim
shoots to point of aim
an honorable mention is a 158 lead with 4.5 grains Unique. Unique will allow a bit more velocity, I do not want to "push" pressures with Bullseye pistol powder.
same ammunition, same day, slightly different velocities. That is one of the screwy things that happens, which is why velocities claims must be taken with a grain of salt. Especially from advertisers.
S&W M64-5 Georgia Department Corrections
158 LRN
4.5 grs Unique lot UN 364 3/9/1992 Brass mixed cases WSP
10-Jun-20 T = 85 °F
Ave Vel = 779.6
Std Dev = 27.4
ES = 109.7
High = 826
Low = 716.3
Number rounds =17
158 LRN
4.5 grs Unique lot UN 364 3/9/1992 Brass mixed cases WSP
10-Jun-20 T = 85 °F
Ave Vel = 794.7
Std Dev = 29.9
ES = 143.7
High = 851.7
Low = 708
N = 24