depends on fast you descend but if 375-405 is making a bar "bend" you have a VERY shabbily made bar, that weight is nothing for squats.
you'd be surprised the kind of shabby bars that float around in older gyms. there's at least two at my gym that'll wobble with 405 and it's pretty alarming. which sucks because they're also the best for squatting and pulling thanks to the way the knurling is set and the diameter on it.
and dude, DK, bossa's put his pictures up. he's hilariously jacked. i'm not sure i believe he was knocking around 315 his first go, but i don't doubt he got there pretty quickly.