I've tried some that belonged to others. They wouldn't save me a single round of ammo nor one minute of my time getting a rifle zeroed. With a bolt gun I can get my 1st shot significantly closer to the aiming point by simply looking through the bore at an object at home or at the range and adjusting the sights than I can with the laser bore sight tools. Irons or optics. On guns where it is harder to bore sight I just use a target big enough that I can't miss at 50 yards. All you need to do is get the 1st shot on paper, it doesn't matter if it is 12" or 1/2" from your aiming point.
The "tools" are only going to get you 3-4" from your aiming point. Figure out the distance you're off, adjust sights the proper amount and the 2nd shot will be at the aiming point. Fire 2 shots at 50, then one at 100 then fine tune and you're zerod at 100 with 3 shots. Then you can start shooting groups.
