>>420641 It doesn't matter if a weapon is good or not, what matters if there's a company with enough financial backing to make it, and enough political backing to lobby it to get used. Jackhammer had neither.
>>420649 It's not wordplay. Before the advent of magnetically charged weaponry, railgun literally meant a gun on rails - or more accurately, a railway gun. They were phased out after WW2, since normal tanks allowed for more mobility.
The Federation had conventional weapons to begin with, they only switched to mobile suits after Zeon introduced them and they turned out to be mad overpowered.
The Gundam, the Guncannon and the Guntank were part of the "V Project" which was the Federation developing the technology for themselves, which lead to the creation of the GM which was the mass-production MS that made up most of their forces.