Black Powder Loadings in 357 Magnum

[SPJ]

I've asked this an another forum so far but will no answers yet from someone with experience. I am curious about what performances are possible with loadings of 357 Mangum rounds with Black powder. I have found some conversations on this site before discussing it. I wanted to see if anyone here has experimented, or knows others who have, with BP in 357 rounds. I have a Winchester carbine and rifle and I'm curious how many grains would provide the farthest effective distance or most consistently accurate groupings of shots. I found that BuffaloArms does sell 357 cartridges loaded with BP, but it does not state how many grains. The consensus I have found so far is that 29-30 grains is the maximum amount that can be loaded, and 25 grains is what is recommended in some sources.

I know that the original loadings for 38 Special included a 158 grain bullet and 21.5 grains of BP. So I am hoping that a modern 357 can be loaded with more powder. So then my question is how many grains of BP, and what bullet mass and or shape, will provide the best performance in either max effective range or accuracy in shot groupings

https://www.thehighroad.org/index.php?threads/powerful-black-powder-loads-for-357.795086/page-2

https://www.thehighroad.org/index.php?threads/ha-loaded-up-357-magnum-bp-cartridges.784916/page-2

https://castboolits.gunloads.com/showthread.php?8616-Original-38-Smith-amp-Wesson-Special-B-P-Ballistics

[Froogal]

I HAVE experimented with black powder in .357s, but it has been too long ago. Don't remember the details.

As far as .38 special goes, I don't know how a person could get 21.5 grains of FFF to fit. I loaded up 50 rounds of .38 special with 158 grain LRNFP over just 12 grains of 3F APP. Shot all of those just yesterday and they worked just fine.

[Cap'n Redneck]

21.5 grains of blackpowder in a .38 Special case would refer to the old style "balloon-head" cases.

[greyhawk]

357 mag makes a neat little BP round .....158 grain LEE flatpoint ...25 grains is about all the powder you will squash in there. didnt chrono it but made a nice sharp crack at the range.

[Crow Choker]

Well according to your first sentence of your org post SPJ, you're asking for response from someone with experience in loading .357 cases with black powder. I have none, but alot with reloading 38 Special, 44 Colt, 45 Colt, and some with 44 Special. In regard to the 38 Spec, I reload with 18.5 grains of FFF using a Snakebite cast lead bullet (Dick Dastardly) that drops at around 160 grains. Good accuracy out of my Uberti Richard/Mason model conversion and Marlin 1894 Cowboy model rifle. No excessive blast, burns well, and normal residue.

A .357 case is approximately 1/8" longer, not sure what the max or best load would be, but as with most metal cased black powder loadings, the rule of thumb is to drop enough powder to where the bottom of a seated bullet would reach, then add enough to get good compression. Nothing excessive, just enough to compress. As with all black powder reloading you don't want any airspace in the round nor excessive compression so trying to play around with less or more with black powder loadings doesn't leave alot for experimentation. Not like playing around in reloading minimum/maximum powder charges as with smokeless powders. A person can experiment using either FF or FFF to see what works best. Have read that anything below 44 calibers use FFF, anything above best results can be had with FF.

I reload alot of 44 Colt with FF black using a Mav Dutchman 200 grain cast lead bullet. Most of the time I use 25.5 grains. I have a few times loaded up some 44 Special rounds with the same bullet using 28.5 grains of FF black. They shot all right but didn't perform any better than the 44 Colt loadings in my Uberti Richards II, Open Top, and Model 66 Yellow Boy rifle, saw no need to use 44 Spec black in these firearms so just use 44 Colts. The 44 Special case is around 1/16" longer than the 44 Colt. Being the .357 mag case is 1/8" longer than the 38 Spec it will of course hold more, the 25.0 grains of FFF you mentioned SPJ might be the ticket, but I'd do the seated bullet height of powder in the case plus a bit more to get good compression. You didn't mention if your shooting goals for accuracy is for Cowboy action shooting, target, or hunting. Just curious. 

[Cliff Fendley]

Just fill it to about an 1/8 inch from the top and compress it either with the bullet or so the bullet sits on the powder. I don't know how many grains it takes for a 357 but that method works for every other pistol caliber round with BP.

[David Battersby]

https://castboolits.gunloads.com/showthread.php?162479-My-foray-into-38spl-black-powder-loads

I have loaded and shot 357 magnum cases in my 1892 Japchester.  It is most definitely accurate but it is not at magnum power levels.  I never chronographed it.
I used unsized Starline brass. Brass that had been fired with full power loads of H110. This helped reduce fouling in the chamber, "blow by", to nothing. I don't have the exact load info near but....
158gr Accurate mold at .360 in 30-1 alloy, DGL black powder lube, Swiss 2F ( don't have any 3F) and CCI small pistol primers.

[cpt dan blodgett]

I would fill case to have between 1/16 to 1/8 inch or compression

[Knarley Bob]

I would fill case to have between 1/16 to 1/8 inch or compression

Yup, as long as the powder is touching the slug, and a little compression is fine, you'll be good to go. Make sure you are using a BP lube also, will make life a lot easier.
Yes.... I'm a Warthog/ Soot lord   

KB