i thought id ask because i bought some .357mag brass because it was cheaper than the .38spl brass(also it was in packets of 100 and not loose in a big box like the 38s so i didnt have to count). would the lower pressures be a problem? if it is i will just load it to light .357mag levels, just thought i try to save a little powder.

You won’t have any problem loading 357 brass to 38 specs.

Use a 357 recipe to load the 357 brass or you could end up doing damage to the gun . You need to use the right loads not start guessing at it . You can look in your manual and find a light load but match the load to the case . To little powder can be as bad as to much .

Are these jacketed or lead bullets? Don't quote me on this but I would think lead bullets can be loaded way lower than jacketed because there's very little drag and it would be next to impossible to get them stuck.
Just thinking out loud because of using lead bullets in a muzzle-loader. To unload, it takes VERY little air pressure on the nipple.
But to be safe, use load data.

_________________________________________
Safety starts with sanity.

ill just load really light .357 mag loads then, i was only going to do it if the was an OK from at least 3 people with experience, but oh well it wont reall ycost me that much more.

It's okay to load them light but it takes away from the fun of shooting a 357 Mag. If you want to shoot something light, try a 22 LR. Have fun, and be safe.

38 loads in 357 are all right to do, especially in light target loads. As far as low pressures in fast powders that you would use in these loads like Bullseye, you will have that gun last forever.

I experimented once with VERY light loads of bullseye using wadcutters, got it to the oint that the bullet would literally go about 10 feet out the end of the barrel. No, there was no purpose in it other than to see it happen.