Well, I'm now a 100% believer in the 223 idea. I wasn't a doubter when there is the volume of evidence shown here, but until you experience it for yourself, it's still a little unknown.
Last night I shot a shmedium bear with my RSS 223/73ELDM @2840.
A boar about 5', stout for his size.
298YDS, sitting off backpack.
He must have got a wiff of me because he stood up sniffing in my direction. That's when I shot him in the chest.
The shot crumpled him, still moving a little, I put another one in him. He went down behind a aspen sprout so the second shot was a guess and hit center shoulder.
The first shot cut the pipes forward of the heart and made a baseball size cavity right next to the spine in the backstrap stopping 1" short of exiting.(entry @ knife point in pic)
The second shot upset @ 1" making a baseball size cavity in the center of the shoulder meat and continued through both lungs stopping under the hide right at the entry of the first shot.
At first I thought the first bullet had stopped under the hide some how.
The damage was definitely enough but not excessive. I lost some shoulder meat and 4" of one backstrap but a 300 RUM "that you need for bear" would have been worse.
Also, before the S2H course, I would not have considered shooting off my pack @ 300 yds.
Last night, after the course, I knew he was dead before I pressed the trigger.
The other thing that actually made me laugh out loud after the fact is how automatic it was having done the S2H course.
I could see the bear moving through a creek bottom towards a big opening. He made it to the opening sooner than i expected.
I ranged the opening, grabbed my pack, dialed 1 mil(mental quick drop), no wind and put the crosshair on him. As soon as he stopped, he stood up.
I fired, racked and reset, he moved broadside on the ground and I sent another one, rack and reset.
It all happened in about 25 seconds.
The minimal recoil of the 223 allowed me to see the whole thing in the scope but I remember seeing the brass in my peripheral go flying like it had been ejected from an AR.
I've put around 3000 rnds through my RSS since January and like others have said, they are stupid fun and very lethal!