Sup! This is the America speaking!
Our muskets were made by me.
Basically the structure is made with craft foam and a lot of hot glue (make sure you have about 100 sticks of mini ones, maybe less if you're using bigger sticks). The main nozzle is a PVC pipe running through the whole thing to the butt of the gun. The foam is offset and bent to make the curved/slightly bent end of the gun. The rings are just painted strips of craft foam. The whole wooden part is just craft foam. Even the bayonet. The bayonet are skewers, coated with the shaped poster board, then another layer of craft foam (safety reasons lols) then duct taped to the nozzle. The bayonet can be made with several different materials but it all depends what you're using it for. For us we were fighting in the skit so we managed to break an earlier foam bayonet, a clay bayonet and also a wire bayonet that never made it out of my house (whoops!). The trigger is clay. There's a wire running through to make it more rigid. It's just hot glued on. Then the whole wood area is painted with out door paint with the wooden texture. Then sealed off with a prayer and modpodge.....Several layers of modpodge (I suggest using a hard type mod podge then gloss mod podge).
For a more accurate musket, I'd use a smaller pvc pipe and I'd get two. Then glue them together (check pictures). So the top pvc pipe would be longer in comparison with the bottom (hidden) one. But how much you need would vary height-wise and how accurate you wanted it. I'm exactly 5 foot. With the bayonet it was about 4'10".
Actually I'm planning to re-make them again one day for visual accuracy (the one on the pictures were the second time I made them).
Tip: when making the base... Just.... cover it with hot glue... ><;
If you'd like... I can just make a tutorial... xD I have pictures.