Highest Critical Strike

Soooo I've been trolling around in custom games for a while because I was bored. I decided to go full AD and see how high of a crit I could get. I sold some items at the end but when I had max ad, here was the setup.

(full) x4 for full crit chance I don't have scaling ad runes, but I had full flat 23 ad or whatever the actual value is Dragon buff x5 Baron buff Max AP shield 21/9/0 masteries

And the total ad was 1613 with shield and w.

Somehow I crit for 5262, not sure how that happened. (was on a small raven-thingy-whatevertheyare) Cause that's like 3.26 times the damage and I didn't have any flat armor pen. Someone explain? I didn't have any blade weaving dmg buff, and havoc should only bring it up to 257% dmg.

tl;dr - I was wondering, with best team comp, best items, all buffs/elixers, runes, etc. etc. what would be the highest crit possible? (excluding , we all know that's infinity mathematically)

edit: It's kind of funny to see a legendary bot.