madsenshooter wrote on Feb 9^th, 2018 at 12:15am:

I recall seeing the name Souper, in one of my case forming books, but can't recall details without finding the book!  Oh, it jumped out at me, thickest book I have!  Book says .25-308 for the Souper.  All I see  in 25 cal wildcats that approximate the 6mm's headsize is 30-40 and .303 wildcats.  But I'll bet somewhere along the way someone made a .25 Swift or maybe a .25 Lee!

Back in 1989, I was messing about with a Lee Navy sporter with a bad barrel.  The old time gunsmith that was helping me said "back in the day, they would have bored it out to .25.  There was a wildcat called the Souper. Just the Lee Navy case necked up to .25 caliber."