It's just an extra then, as there was a MG ammo bin listed farther down, IIRC, the AC2 ammo bin was the first ammo bin listed in the .json file.
Correct, it should not be there and I have removed it thanks to you
I was more concerned that it 'broke' something by not having enough (or worse, any) ammo for the MGs. In this case it literally just makes the tank illegal and 1 ton overweight (until the corrected file is in place). This isn't a game changer, as the Vee can't do anything with the ammo and it doesn't hamper any functionality it should have.
So, it will be part of the inevitable 1.6.2.3 update - but isn't anything to worry over for those that have the current version.
That being said, anyone who wants to fix it - just replace with the attached file (extract the single file and drop into \\BATTLETECH\Mods\JK_VariantsCAB\vehicle folder - you should be prompted to replace the old file).