There are a lot of reviews out there on this item. I checked many. Over 90% highly recommend it. However, I was almost "turned off" by several that stated that you could not boresight a red dot - not true- I was able to check and record the zero of a Trijicon RX09-23 on my AR, an EOTeck 512 on my son's AR and was able to boresight a Burris FastFire Red-Dot Reflex Sight on a Ruger .44mag auto.
It took a little experimenting to do the red dots. They were done indoors - incandescent lighting against a white background with the Leupold's illumination off.
The Leupold got the Ruger/FastFire on an 8" paper plate at 50yds. and took only three rounds and minor adjustments to zero it at 100yds.
I checked and recorded the zero on four other scoped rifles. It worked great on three of the (one with a stainless barrel); however on my 30-06 model 70 Win. the Leupold indicated that the boresight was 25" right of the zero. The vertical was right on.
Having zeroed and boersighted the M70 many tines and fired hundreds of rounds through it over the last 35 years, I knew that was an error.
The Leupold grid is calibrated in inches at 100yds. I checked boersight on the M70 using the Leupold and by looking through the bore at my club's 100yd. range. The techniques differed by ≈ 25". I then guessed the crown of the M70 bore was not machined perpendicular too the barrel.
Subsequent investigation indicated that was the reason for the anomaly. I estimate the M70 bore was crowned ≈ .4 degrees off the horizontal axis. However, by factoring in this error the Leupold can still be used to manage zeros on the M70.
Conclusion: Trust the Leupold boresighter. If things don't seem right check your other stuff.
I have used laser bore sighters. The Leupold is much more usefull. e.g., Use it on the range in bright daylight.
Record illuminated grid zero readings for different ammo types. Then use this data to set zero for a specific ammo or even set zeros for your specific ammo if you change scopes.
Cons: User instructions inadequate
This review was written in the old system and had content requirements that are different than reviews written today.