Is their some trick to getting easy shell or horn I am missing? With the lack of a sawmill for wood production, I feel that it is far easier to obtain a sustainable supply of Bonemetal than it is to start cranking out lamellar.
Well, nothing at all against ironbone, but just to play advocate -- If you're near a pond there's turtles for shell, and my forts tend to be stocked pretty well with both Aurochs and invaders' dead hoof-animals like unicorns, horses, and deer. A full lamellar suit should take quite a few less pieces of material to craft than full ironbone too, and ironbone requires fuel.
edit: Also, just to mention again, our version of wood farming is Kobold Textile Hut -> Strip Wood Stalks. It's just one of those things that developed separately in orc mode vs. dwarf mode. Better than trees in many ways, the yield is not 100% and a lot of the wood is scrap quality, but they grow fast year round, use as much as you need and distill the rest into stalk whiskey. To me it's a little non-intuitive when I play dwarf mode and it's not there
Still a little unclear on the role of atlatls though - are they better than bows against unarmoured? Maybe a good weapon for hunters or arming militia against cavern critters?
The javelins are bigger and heavier than arrows so, they deal more grevious wounds when they do penetrate armor. This balance works out best when you're facing large, squishy creatures. For example there was a version when Dwarves and drow used to invade with VCCs pretty regularly and javelins were great then. In an evil biome I'll generally have a Sun & Stars temple since I'll want morningstars anyway, so i'll have a squad of hammerhead javelin armed atlists if i can spare the electrum, the intended purpose there is crushing rather than chopping up undead.
For cavern patrols i don't really like the base atlatl or bow, because they're helpless at melee, but Falcon warriors (spear and atlatl) seem to be quite good for it. Dragon warriors (composite bow and katana) is too, but the dragon kit is quite a bit harder to craft a full squad worth of gear.
Also, some mad genius in my fort just made an artefact 'blaster musket' - is that different from a normal musket?
An artifact blaster should be a pretty good weapon. That's a new weapon that orcs can normally make only from a complex industry depending on gnomish high tech, metallurgy,and other foreign crafts; it uses gunner skill but fires magic missiles. It's not actually better than a Destroyer's or Gnarled Magestaff at firing missiles, the advantage is just that Corsairs and other gunners can use it, who I figure are more likely to be highly skilled. If you don't have a Heavy Weapons Armory and a gnomish labor cell cranking out diodes, your Arcane Forge can make ammo for him. Since it's quite hard to craft i haven't had a chance to test yet -- i'm interested how it goes.
And one last ranged weapon question - I'm guessing the 'magestaffs' are the ranged Dreamwalker option and the 'sigilblade' for melee?
The main difference is the spell they teach the wielder. The Sundering sigilblade is the most melee oriented, a dreamwalker or mage wielding it can cast Weakness to orichalcum & bloodsteel on enemies. The Destroyer's magestaff gives a ranged, sometimes-paralyzing attack. Bloodcurse causes heavy bleeding, acts as combo damage & debuff. Grappling Ivy is a disabling spell.
They also give access to the two different classes of enchanted ammo that have the chance to impart magical effects. Start with agony for bladeshards and poisonivy for staves, both are safe to friendly fire even at melee range. Some of the spell ammo can be dangerous (corpse explosion, arctic gale).