Andy thats what we do in the industrial electrical field. Get a crimp on ring terminal to fit the # 6 wire and one to fit the # 10 wire with both ring holes the same size. Bolt them together, make one wrap with regular electrical tape, two or three wraps of electrical rubber splicing tape and then one more wrap of vinyl electrical tape.
You can even solder them after bolting them if it make you feel better.
One more possibality is to use a split bolt. It looks like a copper U and has a nut with a foot to compress the wire together. Again use the taping method described above.
Durwood