The reason my "capper" won't work is because the caps were too tight to start on the nipple... one of my nipples fits them fine & i changed to it. the others (nipples will fit soon).. I just purchased these rws 1075+ caps a couple weeks ago.. The tight ones after pressed on blow off on these tight nipples too..(sometimes they stick in the hammer though)... It was my surmise that they would be great as a waterproof fit... There is a problem that negates the tight fit however... When my barrel is filled & the cap plugged,,, water leaks from around the threads of the nipple, (& i use bolt grease on them & the fit is still not good enough to seal off the powder)...