BP subsitute (777) in 38 special or 357 Mag.

[Palladan44]

Can i use 777 fffg pushing some 158gr swaged lead round nose in 38s or 357 cases?

This just would be for fun plinking some bowling pins (just want to show off)

Should i run the 777 fffg through my charge thrower in my dillon 550B without worry?

I understand it should be a compresssed or nearly compressed load to work properly, from what ive read.

Would be fired through a ruger blackhawk 6".

 

[kcofohio]

Here is a video comparing Goex black powder to Triple 7

 

[GeoDudeFlorida]

Unwaxed swaged lead is going to leave deposits in the barrel so get some Shooter's Choice lead remover and be ready to scrub a little. Also, the 777 is "cleaner" than real black powder but it's not smokeless clean. It will foul the area under the forcing cone where the cylinder pin inserts into the frame and cylinder, so don't plan on being able to shoot more than one or two cylinders, at most. I've seen 777 get "spikey" too especially in cartridges with no wad. I place a card wad over my charge, then a lubed wad, to keep fouling under control and reduce the load to something reasonable. Especially if you decide to use a .357Magnum case, which I don't recommend.This site by Hodgdon's gives some good info. They do not list .357Magnum cases and I do not recommend using .357Magnum cases with 777.
https://hodgdon.com/wp-content/uploads/2017/01/muzzleloading_manual_2008.pdf
These guys explain the process:
https://www.shootersreport.com/reloading/Reload-Triple7andPyrodex.htm

 

[.38 Special]

Can i use 777 fffg pushing some 158gr swaged lead round nose in 38s or 357 cases?

This just would be for fun plinking some bowling pins (just want to show off)

Should i run the 777 fffg through my charge thrower in my dillon 550B without worry?

I understand it should be a compresssed or nearly compressed load to work properly, from what ive read.

Would be fired through a ruger blackhawk 6".

Yes, it will work. Fouling is likely to be a big problem.

<Edit> Looks like @GeoDudeFlorida beat me to it.