I know this is going to sound strange... before you invest in another tool, try a good toenail clipper. The one I have makes a perfect flush cut in 18 ga, silver, copper or GF wire every time. I don't use 16 ga, soI'm not sure how well it will work on that. But for 18 and smaller, it's great.
I misplaced my regular tool once, needed to get a repair done quickly, and looked around for something that I could use to cut wire. Tried my fingernail clipper and it 'almost' worked. So, I grabbed the toenail clipper. Worked like a charm.
It takes less pressure to make the cut, too. So, if you are making a lot of them, as I do when I make necklace or bracelet links, your hand doesn't get as tired.