USMC OOB ?

[PlasmaKrab]

It does seem foolish to switch from 25mm to 30mm in the EFV if for no other reason than you now have a separate "one off" ammo supply for this once vehicle rather than having commonality with the cannons in the LAV-25 and Bradley. Or is there a move afoot to up-gun those platforms and make 30mm the new standard?

Could be, could be, I know that I didn't see a single Piranha III (aka LAV-III, Stryker, Coyote) in recon/IFV version with a 25mm A/C. All seem to use the 30mm Bushmaster II cannon, as many CV90 variants do (Norway, Finland, Switzerland, maybe Greece), so that would be the closest you'd get from a future standard.
I also heard many people ranting about the feeble 25mm "pea-shooter", but those were also the people ranting against the Stryker, calling for the Buford and naming the M-113 Gavin, so I don't know how general the feeling is.

Taking a big picture perspective it seem odd that most calibers are standardized for NATO (105 & 120 for tank guns, 5.56, 7.62 12.7 for small arms, etc.) but it seems to be a everyone does their own thing for small cannons.

Mind you, NATO calibers aren't that standard either, the more sophisticated (tank rounds) or straightforward (artillery shells, rifle ammmo) only have some chance to make it, the middle class of small cannon bullets are just right to be produced/bought differently by just everyone wanting to take an edge.
Actually the end of the Cold War kinda put a stop to it, otherwise maybe the dual 35mm/50mm gun would have become some sort of standard.