I had a similar question a few months ago and here is what I was told to do....it worked like a charm!
Take a 15mm open end wrench and put it around the barrel behind the muzzle brake. Take a hammer and tape the wrench underneath the brake and the brake will pop off. They are held on with some type of glue, but it will pop off without a lot of effort. You would then be able to mount a standard front site then. I also had wrapped my barrel with tape so as to not scratch it while using the hammer. I hope I explained it well enough so that you understand. If you're still not sure, I'll post a photo of what I'm talking about.
Sorry, but I don't know what the top of the breach area looks like on a Carbine sport, so I'm not sure if a rear sight can be mounted easily.