The bigger the bore, the lower the peak acceleration, and RAMAC is inherently a "long shove" vs. a specific impulse at the breach.
It absolutely rules out passengers, but doesn't really seem to be a big problem for components.
The much bigger problems are sound/ablation at the muzzle (hitting the atmosphere suddenly at 10km/s...), and barrel life/erosion (big battleship guns got...150 round lifespan. Barrel erosion is related to velocity. The breach of this will not have much difficulty, but the muzzle end probably won't do well. OTOH it's not rifled or otherwise close-fit, and could have "wipers" which are themselves ablative/disposable. Since there's a rocket/guidance package, it doesn't need to be as low-tolerance as an old battleship gun.
(System has been prototyped by Bull using 16" surplus battleship guns in Barbados)