I can't comment too much on the Pulsar N550, although I was thinking of buying one a while back, but I never got the chance to try one out. I wanted something for use on my 22RF for rabbits out to around 60yds, and in the end I decided to go for and addon system; in fact a secondhand Pulsar Challenger with day scope adapter! For the money paid, I was truly staggered at what this little unit could do!! These systems work better with some scopes than others and do need a laser IR to get the best from them, and ideally use them with side parallax, but I took a chance on using a Simmons WTC 6-24x56. With the laser on, if I was using 222 / 223 I could easily shoot at 150yds and it will locate way beyond 200yds!! I have heard differing reports of this addon system (but most are positive), and I may have just got lucky with my combination. Without the laser I would struggle to see my feet, but turn it on..........wow !!!!!!!! Given the eye relief of the system, I don't think it could be used on anything much over 223, although I am tempted to at least give it a go on my 22-250!!
I paid 260.00 for the unit and DSA + 140.00 quite amazed at what I got!
ATB
Tom