Hooligan is right. I've tried almost all of the copper removers and Boretech Eliminator is easily the best I've used. And yes, I used Sweets for a long time. Boretech is better.
I tested it on a rifle that I had recently cleaned. I had gotten all the copper out of it using an ammonia based cleaner, or so I thought. With the Boretech, I got a lot more copper out. A lot.
That said, sometimes a rifle shoots best when it still has some copper in the bore, so maybe you don't want it all removed. That's up to you and your rifle. I've got some of both, some where clean is good and some where clean isn't so good. Took me a while to figure out which rifle was which.