Blunt weapons are rather pointless (pun intended). Anything below full iron armour doesn't warrant specialised can openers, copper spears will do at least as well - and they're somewhat useful against beasts. Since many invaders will have exposed limbs, picks are a decent compromise.
If you want blunt weapons for flavour reasons, all non-adamantine materials seem about equal in usefulness. There are reproducable differences, but they seem to be both minor and complex (what's best may depend on wielder stats, exact weapon and victim. For example, silver often seemed ahead against armour but behind against unarmoured opponents)
Copper and silver made the best bolts next to bronze in my tests, again with subtle difference depending on what you want to shoot (in my tests: bronze against armour, silver against unarmoured flesh). Others reported that steel does well too, they have been disappointing when I tried. Not sure what's going on there.
If you want to get your military kitted out before you have better materials, copper stops slashing attacks reasonably well and it doesn't get much better against projectiles. If weight is an issue, you can supplement it with bone.
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Regarding shields: I don't understand the mechanics behind blocking, but in my tests adamantine shields were better than other metals which were better than wood. I'm not at all sure that copper is particularly desirable.