Originally Posted by big_gun_man
I checked today and the scope is mill/mill, am I understanding you correctly and do you mean that if I sight the scope in at 200 yards with the scope set on 8 power, that the scope will only be accurate using 8 power.
Thanks, you have been a big help.
No, the scope will be accurate at any magnification setting, but your reticle will only be accurate at one magnification.
When you're shooting, as long as you dial in the correct adjustments you will still be on target, it doesn't matter if you're at 8x or at 24x
The difference between SFP and FFP scopes is the usability of the reticle. Becuase the reticle on an FFP scope appears to grow or shrink as you move through the power range, the reticle is accurate at any setting. The reticle on an SFP optic is only accurate at one setting.
Here's a simplified example. Say you're looking at a 1 yard high target at 1000 yards. With your scope set at 24x it takes up 1 mil on your reticle, as its supposed to (1 mil is 1/1000th of the distance you're shooting, therefore a 1 yard high target at 1000 yards should take up 1 mil). Now if you go ahead and back the scope down to say 6x, your 1 yard high target will appear to only take up a fraction of the 1 mil it took up on your reticle at 24x, even though you know that mathematically that target is 1 mil high.
Check out this gif of a Premier 1.1-8x24mm FFP scope. Notice how because the reticle appears to grow and shrink it means the light always takes up the same amount of mils on the reticle.
A SFP scope won't do this, if the scope in the gif was SFP rather than FFP it would mean that the light would appear to take up more and more mils on the reticle as the level of magnification increases.
Here's an explanation of some of the things you can do with an FFP optic at any magnification setting if posted in a previous thread
Some examples of how much easier an FFP mil/mil optic makes shooting:
Say you're shooting your rifle at a target at an unknown distance using an FFP mil/mil scope. You fire your first shot and you see through your reticle that your first shot was about 1.2 mils low and .5 mils left according to the markings on your reticle. Now because your turret matches your reticle, just dial in 12 clicks elevation and 5 windage (0.1 mils per click) and you're right on.
If you know the size of your target, you can use your reticle to very quickly and accurately calculate the range of your target before you take a shot. Say you know your target is 36" tall. On your reticle you see that it takes up 2.5 mils. Knowing that 1 mil equals 1/1000th of the distance you're shooting, you can work out the range with simple calculations. Since 36" = 1 yard, and you know that at 1000 yards a 1 yard tall target will take up 1 mil, you can go ahead and divide 1000 by 2.5 which gives you 400 yards.
If you're shooting at say 600 yards and you didn't see the impact but your buddy tells your shot was off by about 9 inches and you want to correct this. In your head you know that a mil is 1/1000th of 600 yards, or .6 of a yard. Knowing a yard is 36 inches, you work out that .6 of a yard is 21.6 inches (I do this by dividing 36 in half to get .5 of a mil or 18 inches, then adding on 3.6 inches for the extra .1 of a mil to make .6, but you can get here lots of ways). Dividing 21.6 by 10 gives you 2.16 inches, which is what each of your .1 mil clicks will equal at this distance. You proceed to dial in .4 mils to bring you to within .4 of an inch of the correction, which is well within the shooter and spotter margin of error.
You can still do these things with an SFP optic, but you can only do them accurately on a single power setting.