If it is just the fiber optic part of the sight that is broken they can easily put I new one on. I would have store/factory take care of the sight for you. But the concrete stuff is just the powder residue, there is a lot of it if you compare it to smokeless powder. Just keep shooting, usually after 3-5 shots fouling gets bad and a few swabs are necessary. I try to shoot as many times as I can until I get a slight hang fire, then make sure I clean before I get to that point in the future. I hunt with 150 equivalent grains of pellets (3), but when I am just shooting I usually only use 2 pellets / 100 grains. point of impact is only marginally different