What if the barrel is loose do it need to be tighten?
The guide rod and barrel are separate and distinct also the barrel on a sig is free floating so it should not cause you any problems with the laser. The laser replaces your guide rod. If your barrel is loose with the slide all the way forward you may want to check with a gunsmith because that would not be normal. The barrel should float only with slide all the way back. The laser has been great and I have been very happy owning it.