What's too long?

[jon lynn]

When does a barrel get too long?

What is the maximum before it becomes silly, or counter productive? I mean for a varmiter, or long range shooter.

Let's stick with some basic cartriges for my question:

.223 Remingtom with 55g bullets

.308 Winchester with 150 grainers

and a .30-06 with 200 grains for the old 'bean field' mentality.

Jon