I don't get why people hoard ammo. Realistically I play offensive, usually 7-15 kills by the final top 10 if I get there, never go above 200 ammo for a primary AR. It's just unnecessary, you are pretty much never going to have to waste more than a clip on 1 guy, half of the fights in either medlong or short range are all 10-40 bullets anyway.
Like occasionally I run into people with level 3 backpacks with nearly 350 5.56 ammo. You will never need it and you would be better off having enough room to quickswap weapons while keeping attachments.
Even just yesterday, went crate hunting, 1st crate landed on pretty much the north shore, while the plane did the E-W path in over the bridges and the first circle was already on the bottom island. Someone go there first, they had an AWM, killed them with my Kar, ran to take the weapon, quickly swapped it, while keeping my sniper attachments (super rare to begin with) and just as I got it swapped, from a cliff I got blasted by a guy with a scar. Literally managed to take cover with 10% HP left. Had I dicked around even 1-2 seconds more I would have been dead.
tl;dr the chance of you using even 200+ ammo without having a safe resupply is much lower, than the chance of a quick weapon swap from a corpse saving your life from someone sneaking up on you