So heres the barrel from the Miller I bought that might be for the  the Wolf Decapper I got also. Anyone have an idea?  Looks to be 357 Max parent case.A 357 mag case drops in. I pulled the barrel to chamber cast. also action hung up a little in cocking ,slight scratches on block so need to be taken down A tad to operate smoothly.  I'll be putting a 32 miller barrel on this action . so this barrel will go down the way for sale. Never fired. I Thankyou

I have a similar case on my Hoch, with a 30 cal RKS barrel. 

I first made it as a 30/30 Wesson and then, ran a a 223 reamer into it, leaving a .31 long neck. The Schwartz looks like it has a steeper shoulder angle and shorter neck, than my 23° shoulder.

There were two 30 Schwartz cartridges, long and short.
One was a 30-30 parent, the other 357 Max. Both are a straight taper from base to neck/bullet. Very similar to a 32-40 but shorter, so a lot more taper to the smaller bullet.

Many different variations of both 357 and 357 max necked down to 30 caliber. As a rimmed version of many 223/222 based cartridges. Even a 30 Luger.

A straight taper, 357 Max, to a 30 cal neck, would be a basic 30/30 Wesson. I did mine that way so, it with be a original BP chambering.

Does anyone know how a Brewer shaped?

Rkba2nd,
Not sure which came first, the short or the long. The idea in making the cartridge was a smaller capacity case for smokeless so maybe the 30-30, then the 357 donor? Maybe at the same time?

I have formed both by using a shortened 32-40 die. Cutting them off at appropriate base diameters. Both versions seemed to have suffered the same problem in that the reamer did not have a 200 line, the short straight section at the base. I needed to size the cases all the way to the rim, then knock them out of the die.

Below is a 30-30 Wesson next to a fired 30 Schwartz. Note the very slight shoulder on the Wesson cartridge. You can chamber a Wesson in a Schwartz chamber, but not the other way around.

Barrel maker unknown, this is a 12 twist  27" . 1.250 breech, .950 muzzle.  I know it's not a cheap barrel,the estate was multi million dollar!   So cut off the threads , a 26" barrel.  What 30 cal bullet would be used. It will be up for sale.