If I were to do this using a .358" groove barrel, What would be the maximum weight plain base bullet for a smokeless round? Target would be 1350-1400 fps. BACO shows a 1.45" long 340gr  but I'm wondering is this bullet too heavy for the 357 max case size. Looks like it would require about a 11 twist barrel. I am sure the old 38 Ballard Extra Long used much lighter bullets than what I am hoping could work.

I have a 357 Max on a LW with a 28" long 20 twist barrel.

14.0 gr of 4227 with a Lyman 35875 or a 358315 mold (both 208 gr) I get 1437 fps , shot breech seated.

That load would work in a Ballard but, I wouldn't want to go much more.

SAECO makes a 200 and 245 gr molds. I'd hold it at 13.0 gr with the 245 gr bullet, reduce loads 1.0 gr for fixed loads.

It's all original with a rebored 32long  barrel.

The load I sited is a fairly low pressure one.

With the GC bullet, I ran it to 1830 w/o any pressure sighs but would not do that with a Ballard.

I call it a 38XL and not a Max but, you have to use the Max reamer😊

I bought this LW, in about 1990, long before they got so weak!

At that time it was chambered in 357 Mag and thats what Frank DeHaas included as safe for the LW and no one that I knew had said anything about them being so weak as they are supposed to be today.

I only shoot it a couple of times in 357 Mag before rechambering to Max. I had no intention of running 50k pressures but, I felt comfortable taking it to the 37k level using pistol primers and there flattening to judge it by. I had no issues at all and I think that the Max has an excellent pressure to velocity ratio. Others will disagree with me but my rifle is still fine.

But I will always call it a 38 XL now that the internet has made them so weak.

Browning/ Miroku made the originals weak.

When the low wall was reintroduced by Miroku in 1995, it was available in 223, 243 and 260 Remington, up to 60,000 psi cartridges. A lot of people started pushing the limits of the originals with poor results.