On all of mine get it all built, then disassemble it to brown the parts. I brown the barrel & sights separately, then put it all together. On the vent liner, if it is removable take it out & put in a allen screw the same size with some teflon tape on it. If it is non-removable, take a round toothpick & break it off & tap into the vent hole shugly. Now brown away.......