a slight correction here; the G1 is no older than the G7. They were developed at the same time and by the same guy, E.D. Lowry of Winchester/Olin. The G1 has been the default drag model that has been in use ever since as sort of a compromise standard for everything, including more modern design bullets that don't accurately match the resulting trajectory shown by that model. Berger's trying to change that, and educate the current generation to use the proper drag model, and enjoy the benefits of a truly accurate trajectory prediction.
I'm sure Bryan's link explains a ll this in his usual detail!
A little history . . .