Yes, in fact, if you notice "size changing weapons" being used by D'Orcs or demons, it's almost guaranteed that that weapon is part of themselves.

Notice how the Rod of Tomas/Wand of Orcus doesn't change size? That's because it's a real object.

Remember the D'Orcs practicing with giant oversized weapons on the Isle of Doom? Those weapons were parts of themselves, no different than giant claws, or even energy weapons.

Remember Tom's fire blasts in book 1? No reason he couldn't do those and make them seem to come from a ray gun or something. With enough skill and practice a demon can use any of their natural abilities in alternative ways/deployment methods. The limit being, if you can't do it, you can't change form and do it. So if a demon doesn't have any ranged attacks (energy blasts etc) then they can't shape change and have a gun. On the other hand, if they can shoot their claws (and grow new ones), or spines, or spikes from their body, they could shape change and have a gun that does that for them.

Also, Hilda's magical armor and weapons that grew and shrunk with her? Same thing.

This is in spoiler because it's going to be even more obvious in the future when Arg-nargoloth really gets into battle alongside Raga-nargoloth. But it has happened already, some people probably didn't realize this.

Also, at the Citadel, you may recall that Beragamos is "incarnated" he had to do that to get through Lenamare's wards in Freehold. Therefore, he can't size change or shape himself a magical weapon since he has a real, physical/material body. That being said, I am sure he has summoning rituals and chants that can bring him real weapons, and/or magical spells to create temporary holy weapons. There are clerical spells that can do this, pretty common in fact for Tiernon's priests to conjure non-real/material magical swords and maces and such that have a mana cost, and which disappear when the spell is up.

But that's different from reshaping yourself into a weapon. There is no real mana cost for that, other than the mana used to change/hold your shape and or needed for an energy blast.