When and why did the 30rd mag come about?

[Iraqgunz]

When I enlisted in 1986 my first issue was an M16A1. 30 rounders were already well into the system at that time.

M16A2's were still not full integrated at that point. I remember seeing 30 rounders as early as 1983.

I've read somewhere that we didn't start using thirtys again until the round burst came out. I'll try and find the source but wanted to see if any of you guys have seen the same writing. Apparently because guys were wasting too much ammo fa with thirty rounders.