The human eye is better able to recognize colors in the green spectrum, so a green laser is more visible under bright light conditions.
We recommend removing your muzzle device and attaching this directly to your barrel to insure the boresight is centered as the flash hider A) might not be magnetic (aluminum for example) and B) may not be perfectly even with the front of the barrel. You should not fire the gun with this attached, the boresight mounts to the front of the barrel. Maximum sighting distance would essentially be as far as you can still see the laser.
Yes, it could be used on a muzzle loader
Per Wheeler, "centering the bore sighter on the muzzle is not critical because the laser is precisely projected down the bore line. Each professional laser bore sighter is hand tuned during the manufacturing process. A series of set screws gets the laser aligned properly and once its set a hardening epoxy is installed inside to make sure that your laser will never come off precision alignment."
It just magnetizes to a flat end of the barrel and you will have to just eyeball its centered when putting it on. The Professional Laser Bore Sighter is designed to get the sight on paper at 100 yards not to get the sight perfectly sighted in.
It will work on handguns provided they have enough metal exposed on the end of the barrel for the magnet to find purchase on it.
Yes, it can be used on shotguns
Yes it will
Yes it will
We don't suggest using this laser beyond 25 yards