Your best powder for 38 sp and 357 mag for use in Carbines.

[R-71]

I’ve been using a lot of HS6. It works well in almost every pistol cartridge that I load for. 38, 357, 44 special and magnum, 45 acp, 45 colt and 480 ruger.

[Froogal]

I was using Trail Boss but that seems to be no longer available, so I switched to 4227. I think I like it even better.

Six shooter or rifle. Makes no difference. .38 specials all get loaded the same.

[AlaskaMike]

Since Lovex powders sound more available and less expensive for you, I'd just recommend you stick with them.

D032.03 (sold here as Clean Shot, also known as Accurate #2) would be ideal for .38 Special. D036.03 ("Auto Pistol", aka Accurate #5) would also work well, and would probably give you a bit more velocity.

D037.02 ("Heavy Pistol", aka Accurate #9) is excellent for .357 magnum. D037.01 ("Major Pistol", aka Accurate #7) also works very well in .357 mag, but you won't get quite the velocity as you will with D037.02.

[braddock]

Thanks, Mike. I've been checking out the Lovex inventory and, perhaps more importantly, what my LGS has in stock.
They have o/d on S040 which is intended for 22 hornet or 30 M1 carbine but is at the similar burn rate to 4227/H4198/W296 and N110. They list 44 mag loads for it so I've sent off an e-mail to Lovex asking after filling 357 mag and 30/30 with it as it's on blowout due to not selling at the GS.
The GS also has D036, D073.1 and D073.2
I have enough 38/357 ammo to last a few range trips and enough powder to reload them twice more so I'm in no great rush to get some more it's just I prefer to have stuff on my shelf as opposed to the GS shelf.
There's plenty vihtavuori N110 around but it tends to be as expensive as Hodgdon and Winchester powder and I've never really had clean burning with the Vh powder in my 308 though everything else about them eg consistency in loads is excellent.