I've heard Glock Mags will melt into puddles of black plastic if left outside in 95 degree temps
Not an issue. I lived in SW OK for years. Summertime temp reaching 100+ was common. Never had a problem with ammo. Even with the car closed where inside temp could easily reach 120+ I never had a round cook off. Now I will admit I've burned the Hades out of myself with a hot frame when I laid my arm against it!
Do a Google search of Youtube and look for Mythbusters exploding ammo. They had fun trying to get ammo to explode in an oven.
I've had mags & ammo in my GHB for years. I wouldn't leave ammo or a charged mag laying on the dash in the HOT South Carolina sun. But, it shouldn't be any problem in a range bag or GHB.
Is there any Kydex in this story?
Let's put this discussion to bed. Here is the SAAMI recommendation on ammunition storage, but please read the entire item as it lists many different storage conditions from wharehouses to auto trunks. It should also dispell some internet myths we all have heard. Also note the address at the bottom of page one Ironic?
After reading, make your own decision as to how best store/secure you ammo.