I am assuming they are iron. I cannot see any bronze pieces, any wrought-iron guns or any breechloaders. That, and the rounded cascable buttons puts us after 1600. No sign, as you say, or gun loops or carronades, so that puts us before 1800. Guns with the trunnions lower, rather than at the medium point, tend to be earlier in this period, more 17th or early 18th century. Hard to tell but the guns seem to be short-ish and medium to small calibre, so more like a substantial armed merchant ship, privateer, slaver, that sort of thing. Can't give a nationality- England and Sweden were flooding the world with cheap cast-iron guns, and they were being used on French, Dutch, Spanish and Portuguese ships as well as their own nation's vessels.
You can't really tell without lifing them and cleaning them and that is an awful lot of money.
Smithbrown