Lets Talk Open Barrel Crimpers - Reviews and Discussion
Sometimes the AWG the terminal is supposed to be for is a little big for the particular wire or wire insulation we're using. It doesn't help that SAE gage wire uses larger strands and so has slightly less cross sectional density than the same AWG stranded wire. And insulation thickness can vary quite a bit too depending on what its for and made of.
In the 60s the smallest wire Chrysler used was 18 gage (SAE), but at some point they started using 20 gage for circuits with lower loads - probably to save space and maybe some pennies too.