From the floor or was it with straps with the bar raised in a power cage? If that is from the floor that is some sick strength. Five sets of five reps with 500lbs is incredible. What's your single? 650lbs?
Weird thing for me is that I've done 405 for 15 from the ground, but most I can remember doing on rack deads with that is 12. I would place the safety bars so that the weight bar is about 3" below my kneecap (i actually just busted out a ruler to see how far down the spot on my shin is where I liked the bar to be. LOL I'm a nerd!) I find this makes it pretty much just a lower and upper back/rhomboids/trap builder, and keeps my ass and hams mostly out of it. Doing them that way also made sense to me, bcuz I did deads on back days.
I was a very strong squatter from day one (likely from years of skateboarding right up until I started training), and my ass grows just walking past a squat rack it seems, so I stayed away from deads, and did squats with heels on a board and knees close. I never did any type of deads until Francois had an article with him doing them, and read why.. which was to keep the glutes out.
Someone gave me shit about doing rack deads one time...I was either doing 455 or 495...495 is the most I've done for reps ...don't remember for sure if that's what I was doing at the time though; anyway, they said I couldn't do what I was doing from the ground. So I said let's start training back together, and we'll find out. Took me a few workouts, cuz it is different in how you set up, and start to pull. Eventually though, I did the 405 for 15, and that pretty much proved to me I could do the same, or more on the floor vs. racks if I kept at them. I've gone heavier, but I don't recall for certain if I did 5 plates or 4 + a 1/4 each side to claim one as fact.
On top of the big ass thing, full deadlifts from the ground have always scared me in regards to tearing a bicep. The way you have to set up and pull up and into your bottom shins felt much more strenuous at my lower bicep and along the distal tendon vs. when I would do racks as the bar is already right up against my shins. Maybe it's cuz I'm short and/or how I'm built structure-wise, or it's just because of how I did them from the ground never really perfecting the movement that way? IDK?
Regardless, I think Matt's the clear victor overall here it would seem. I do get kinda bummed out that during "my time" cell phones were just becoming a thing for people other than drug dealers and celebrities, and there were no camera phones back then. As much as I get pissed off these days about people and their fuckin phones/selfies in the gym, I really wish I had some of those moments captured. Without them I'm just a guy "that used to be"

Man, I hated those fuckers when I was young. Circle of life I guess.
