Well, I can't say as I'm the proud starter-offer of a new thread with this title, but I suspect there is plenty of fodder out there to feed a beast with this name...
So, to start it off: After lovingly cleaning my Bushy 450b this evening (did I mention I love this thing?), I decided it would be a good idea to put one of those little black Hobbit rubbers (Birchwood-Casey's Barrel Cots) all the way down over the Izzy muzzle brake currently in use, to maintain the barrel's pristine condition.
Not being able to resist the temptation to fool around with any weaponry within arm's reach, I stuck a couple of 450b rounds in a SS mag that I had been trying to smooth out to keep it from scratching the brass so badly. Chambered the first round, yanked back on the charging handle and...no movement. Stuck like a...well, you get the idea.
Spent the next ten minutes unsuccessfully trying to dislodge the chambered round, saying words my mama never taught me, while considering how I was going to pry the BCG open without wrecking a brand-new rifle. Just before getting onto the forum here to ask how to pry open an AR action, while simultaneously looking like a complete goober, I noticed the barrel cot was looking a mite puckered up. Light comes on, and goober factor drops way down...
Seems a nice tight chamber plus barrel cot covering all access to the atmosphere equals "stuck" round.
Luckily, no one was watching.