These older snubbies were sighted in for 158 grain bullets. I have shot tens of thousands of rounds of 158 LRN, LSWC, (did not make much of a difference) with 3.5 grains Bullseye in snubbies. This load is accurate, shoots to point of aim, is not +P so it is appropriate with older revolvers.
You can see the various revolvers I used over the years, the velocities with all the different primers and bullet shapes. Overall changing cases, bullet types, and primers did not make much of a difference.
Code:
Colt Detective Special mfgr 1963
158 gr LRN 3.5 grs Bullseye thrown, CCI primers mixed cases 24-Jul-99 T = 100 F !
Average 751 fps
Standard Deviation 32 fps
Extreme Spread 90 fps
High 805
Low 715
Recorded shots 22
158 LRN 3.5 grs Bullseye WSP Mixed cases 8-Jan-06 T = 52 F
Ave Vel = 675.9
Std Dev = 18.6
ES 96.18
High 723.9
Low 627.7
N = 50
158 LSWC 3.5 grs Bullseye WSP Mixed cases 8-Jan-06 T = 58 F
Ave Vel = 706.8
Std Dev = 15.55
ES 65.87
High 742.9
Low 677
N = 50
Colt Detective Special mfgr 1974
158gr LSWC 3.3 grs Bullseye CCI 500 primers, Dillon Loads 17-Oct-93 T = 65-70F
Ave Vel = 682 fps
Std Dev = 33
ES 96
High 733
Low 637
N = 6
Colt Cobra 2" barrel
30-Jan-05 T = 42 F
158 gr LRN 3.5 grs Bullseye thrown, Fed 100 primers mixed cases
Average 696.6
Std Dev 20.49
Extreme Spread 72.93
High 745.5
Low 672.6
13 recorded shots
Taurus M85 B2UL 2" Barrel
158 LSWC 3.5 grs Bullseye thrown, Mixed Brass WSP 11-Dec-04 T = 54 F
Ave Vel = 686.3
Std Dev = 13.63
ES 58.48
High 718.8
Low 660.3
N = 30
shot little high and centered
158 LRN Master Factory Ammo 30-Dec-04 T = 56 F
Ave Vel = 698.2
Std Dev = 20.56
ES 105.8
High 753.5
Low 647.6
N = 50
shot 6" high centered,until barrel leaded
158 LSWC 3.5 grs Bullseye Mixed brass Fed 100 30-Dec-04 T = 56 F
Ave Vel = 706.2
Std Dev = 23.45
ES 81.94
High 748
Low 666.1
N = 48
S&W M638-3 Airweight Bodyguard
148 LWC Lead 2.7 grs Bullseye thrown Mixed Brass WSP
18-Mar-07 T = 52 °F
Ave Vel = 611.6
Std Dev = 22.04
ES 75.92
High 648.1
Low 572.2
N = 25