Is the weight on 12.7mm ammo supposed to be 0.01? Wiki even lists it lower at 0.0064.

The only other ammo that weighs that little are BBs and .22LR.

10mm 0.033
9mm 0.029
5.56mm 0.026
5mm 0.017
.50mg 0.25

I'm guessing the decimal point was set wrong and it should weigh 0.064 give it 6.4 lbs per 100 bullets?

It was probably a typo, but it was for the better IMO.

12.7mm is rare and expensive, and only 2 weapons use it. Makes them excellent choices for hardcoe.

I'm doing an EW play through, and that ammo weighs a ton. Super light 12.7mm just pisses me off.

The GECK lists it to be 0.0064 weight. So if not intentional, yes, probably a typo misplacement of a decimal.