Why linked ammunition feeds become risky as shells grow

Could a rail-fed, linked ammunition system work with shells as large as six inches?

Around three inches is the suggested limit, because a larger round's accidental detonation could cause severe damage; a carousel is preferred for larger ammunition.

A proposed rail-fed, linked system for six-inch rounds raises concerns about both movement and explosive content. The suggested practical ceiling is nearer three inches. The judgement depends on the damage one round could cause if it detonated accidentally, even if that event were unlikely. Above that caliber, a carousel is preferred as the safer handling option.