I've thought about something similar, such as a .223/5.56 case blown out to use .358 bullets, seated to mag length. Like the Blackout, it could use the same bolts and magazines as a 5.56. Should be an effective round with good killing power.
Dang, I knew I had thought of the .350 Legend, years ago - there's the proof
Pity they apparently won't run in 5.56 magazines
Yeah I had done the same thing before this .358 herrett, still have a couple dummy rounds made from straightened 5.56 cases, they look kinda cool with an old school 200gr RN bullet seated in them.
It can feed from 5.56 mags - magazine modifications are the same as needed for this 358 - just remove the ribs. In a metal mag I mill out the rib section; in Pmags (for 5.56 cases, not the 6.8 case I'm using for the Herrett) you can file out the rib from inside. They work great once that's done. I'll post a pic later.
