You've got some good replies here. I have a new Winchester Deluxe and have been working up loads for a while. I have a lot of data but here is a summation (test firing five-shot groups at 50 yards). NOTE: I never give out load data except for sources and advertised velocities - you'll have to look that up in a trusted source. For .38 Special cast bullets: W231 (which is HP38), using 154gr .358 bullets cast from 20:1 at 906fps advertised Lyman 47 pp 388 resulted in 1.070". Next best was Oregon Trail 158gr LSWC .358 using TiteGroup at 920fps advertised (load listed on the powder bottle).
For 38 Special jacketed bullets: Unique behind Speer 125gr JHP (#4013) at 980fps advertised in Speer 13 pp 521 for a 1.019" group. Second was W231 with Hornady 125gr FPXTP (#35730) at 820fps advertised Lyman 47 pp 386 for a 1.225" group.
Here's where it gets interesting. So far, cast bullets don't do well in my 1873. For cast .357 loads, first was AA7 pushing a Speer 158gr SWC (#4624) at 1125 advertised in Lyman 47 pp 394 for a group of 2.054". Second was Western Nevada 158gr LSWC using 2400 at 1422fps advertised Lyman 47 pp 318 for a 2.563" group. I find it frustrating to load cast bullets for the magnum. Some test loads turned in groups exceeding 12" while the same propellant using a different bullet got under three inches. So far, I find that jacketed bullets work best for the magnum.
For .357 jacketed: 2400 sends a Sierra 125gr JHP (#8320) at 1400fps advertised in Sierra V pp 760 into a group measuring 0.654". Second was W296 (which is H110) using Sierra 125gr JHP bullets (#4013) at 1210fps advertised in Speer 13 pp 528 for a group of 0.739". Many other loads tested resulted in groupings of around an inch, give or take, with the best load for Hornady 125gr XTP bullets at 1.285" using 2400 with an advertised velocity of 1700 in Hornady's #11 manual, pp 701. All of my Hornady bullets like 2400 and H110 (which is W296). Worst group was 2.192".
I am now testing 140gr and 158gr jacketed bullets. My research is that the best propellants for the 38 are Bullseye, W231, and Titegroup. For medium .357: Unique, Power Pistol, AA5, and HS-6. For top power .357 loads: W296 (H110), Blue Dot, and Enforcer. I'm still testing all of these. Regarding copper coated bullets, stay away from Berry's in the 38 Special as they are very difficult to make function in the 1873 toggle action, often getting caught underneath the bolt rod and requiring innovative techniques to remove the lodged bullet. I hope all of this helps and apologize for the late response. My wife has alzheimer's and it's very difficult to get on the computer (requires constant attention) yet alone getting to the range... Take care - mj
