As a person who originally developed this cartridge about 5 years ago and built rifles to fire it , I find some of the comment interesting . I based the case on a expanded .223 case as they were free at the time . Winchester made their base about .008 larger so you had to buy their brass . The rim is the same size . I used a .355 barrel blank with cheap .357 pistol bullets . One reason I made the round was the poor performance of sub-sonic 300 BO on game . A good load was the .357 Hornady 180 XTP , as it was made to expand at pistol velocities it worked well at sub-sonic . Starting at a much larger .357 dia , it expanded even more . Loaded up to 2150 fps you then had 30/30 type performance out of an AR-15 . After building a few AR's I switched to bolt rifles . With a small action .223 rifles as a starting point you ended up with a small light weight rifle with low recoil , low muzzle blast but very good performance on deer and pigs out to 150 yards . A lot more penetration and hitting power then you would expect . In the end with the bolt rifle I had a very handy [ kids and ladies really liked it also ] hard hitting medium range rifle that used much cheaper components . Free cases , cheaper bullets and less powder . Every person I built an AR or bolt rifle for really liked them and said they worked well on game . I like my small bolt rifle for hiking around for pigs as it carries so well . My AR with a thermal also works very well on a herd of pigs at night . Many shots , less muzzle flash and noise , low recoil to stay on target , less chance of a ricochet with the pistol bullets . But after developing the cartridge , lots of load testing , 5 years of field use in different types of rifles by many people I may not know as much about it as someone who just imagines what it may do .