Like for instance, on my rifle I have it zero'd to hit about 2.5" high @ 100yds and I just point the crosshairs on whatever I'm shooting at all the way to 300yds. So if I wanted to go to say 550 yds, and I start dialing in elevation on the scope, do I just dial it back when I'm done for my initial zero? And what does a scope that has a "resettable zero" or "zero stop" do for me?
The resttable turrets means that after you have the scope zeroed, at whatever distance you desired, you can (through some mechanical means-usually losen a screw/screws) and turn the turret till the numbered "0" lines up with an index line on the back of the turret housing (from the shooter's perspective) then tighten the mechanical release back down. That way you don't have to count clicks and can actually use the numbers on the turrets for adjustments and as a way to go back to your initial zero. A zero stop is just a luxury, it keeps you from dialing back down past your initial zero. Just another way to be lazy.
If you are dialing for an extended distance that requires you to turn the turret past one or more full revolutions, you can lose track of how many times you have turned it. There are also lines under the turrets on the housing (on most scopes, these are called base lines) that let you know how many revolutions you have dialed.
Dr Vette has a point, sounds like you don't know where you are really sighted in. You are kinda using a max point blank range type of shooting. This is where you sight your rifle in to hit a specific sized target out as far as posible with your rifle/load while aiming center mass of the intended target.
Example: Lets say a deer has an 8" target kill area behind the shoulder (just an example...). You sight the rifle in so that the maximum ordinance of the bullet (max-ord is a projectile's highest point in it's trajectory or flight path) is not higher then half the target size when aiming center, in this example 4". The max point blank range would be where the bullet drop would hit 4" lower then center. Some guys do this because they know they just have to aim center mass and can hit at the furthest range their rifle/load is capable without having to compensate for bullet rise or drop. Lets use my old 30-06, go to
JBM - Calculations and hit trajectory. All I did for this example is punch in .308 cal/180gr bullet/.474 G1 BC for the partition/ 2700fps (what my rifle does), go to the bottom and change the vital zone radius to 4 and checked zero at Max point blank range (I didn't change anything else guys as this is an example so don't tear the data appart
). I get a MPBR of about 300 yards with a max-ord at 150 yards. I can aim center mass on a deer all the way out to 300 yards and expect a kill (not counting any wind compensation, but that is another subject).
That's just one technique.