The way i see it say there are different amounts of items. There are infinite regulars There are 100 uncommons There are 50 rares There are 5 legendaries If you got multiple engram that gave rare items, you have a chance of getting that rare again and again until you have each one crowdin your inventory If you got a legendary 10 times theres a chance you could get every legendary or the same one each time. I know this example might make no sense but it's all random the game even says so. But the way i see it, switch those unwanted guns to a lower class character you have. Much easier. It's frustrating, but it could be worse. You could have gotten a 1000 light legendary armour for a hunter when your character is a Titan. (Thats just an example though)