It makes a good question. But, I have as many co workers have left ammo in car trunks, plastic boxes, factory cardboard, metal, in magazines, in vehicles such as cars, SUVs pickups and boats. I bet many other cops and military have also.
And when taken to the range or else where they fire.
As for weapons: The departments 12 ga and .308's sat in the gun locks inside the vehicle or in trunks. I had both, all of them were fitted with limb saver recoil pads. Those pads melted from the heat, after a few years they got replaced. Ammo was shot up normally on a yearly qualification.
Another note not asked: Because motor officers and like me boat operators may have the service guns, ammo and spare ammo exposed to rain all day. How does water affect ammo?
I did a test with 38 spl ammo both factory and handloads. I keep 24 rounds under water for 5 minutes. I wiped them off and shot everyone without any problem.
My grandfather worked on a dredge in the Columbia River many years ago. According to my father a sealed metal box of M1 3006 ammo once was brought up. It was marked 1940 something AP ammo. I used the key to open the box, just like a spam can in 2015. The ammo looked ok, I fired a bunch clips of it in my M1. All fired as should. (AP stands for armor piercing). I gave the opened box and 2 bandoliers to a friend that owned a gun shop to display.