I figured out a super-easy way to make dome darts using only hi-temp hot glue and some washers. I can't do gravity domes with hi-temp hot glue, neither can I roll them easily, so I made some using surface tension.
I have a video you can watch here:
Or, if you don't like long, boring, terrible videos, I will describe them below.
Basically, all you have to do is take your washers, lay them flat on a surface, and fill them with hot glue. The molten glue will form a dome shape over the washer, just like a drop of water. Only bigger. I would suggest taking wooden sticks or short pieces of nail and gluing them into the domes, so you have a peg you can stick into the dart. The video shows how to do this without making death darts. That way, you can apply some hot glue to the peg, and then let it cool off before pushing it into the dart; also, the peg helps you center the dome on the dart.
The video also describes how to make double-washer darts, but I wouldn't suggest that unless you've got a really high power gun.
I don't have any "normal" guns right now, so does anybody want to whip up a batch and do some range testing?