Originally Posted by azsugarbear
We often use the terms "focus" and "paralax" interchangeably, but this technically is not the case. I believe Dave King has a good explanation of both at the top of this forum heading.
I've got one of each...
My Burris Signature 4.5-14x50 has an adjustable objective for parallax adjustment. Everything is in focus no matter where you look at any power magnification. Parallax changes when you turn the end of the scope. Unfortunately, that means you can're really use a flip-up scope cover. Won't be making the AO scope mistake again!
My cheap side focus Simmons 6-18x40 (that actually has "SF" in the model designation) changes focus with the side knob. In fact, if I focus it at 50 yards, I can't really even see the target at 100 yards. Can't tell if the parallax changes much - i haven't shot it beyond 100 yards. Basically, it's worthless for quick shots at varying distances (which is okay since it's on my bench .22). Luckily, you only have to turn the knob a few millimeters to range it through it's full focal range. However, that makes it hard to "fine tune" the focus. Honestly, if your focus is off by 10 feet, the target will be blurry. Also, even at 6x it's tricky to get your eye in the right position. The eye relief has a range of about 1/4" outside of which you can see nothing. Also, the reticle is rotated about 5 degrees. It was a very low price, but I won't make the "cheap scope" mistake again!
Next scope will probably be a Conquest or a Vari-X III to replace the Simmons. I'm keeping the Burris on my .300 win mag model 70 for now. Once I get a "real" long range gun, it's probably getting a Nightforce. My dad has a NF 8-32x56 on a Les Baer .308. I'm seriously considering getting the same combo, but probably with a 5-22x50.