In response to The Hermit.
Heavy brush and cover is an excellent argument in favor of using optics, provided they are well suited to the task. The guy with a 4-12x scope is probably hurting himself. The guy with a fixed optic from 1.5x up to maybe 4x is helping himself if the optic is mounted on his firearm so that it fits him and works for him.
I have shot deer in the kind of cover you see in the background of these pics, out to about 50 yards. In one case I saw the deer without optics when it stepped into the cover. Once inside I couldn't see it without the assistance of optics. I could see it with binos, but not without them. I looked at it with binos, kept my eye on that spot when I put down the binos, then mounted the rifle and presto, venison in the crosshairs. The scope was a 2.5x Leupold IER Scout scope.
This is a pic of my dad carrying my oldest across the grass burrs to his first deer when he was 6 years old.
Here is the boy a little later after we tagged and photoed the deer and were getting ready to get the truck.
You can see the heavy cover around the area and the whitetails and mule deer love to hide in that stuff.
You still don't believe me? Let's look at some more pics.
These muleys aren't even in heavy cover, but they would be hard to spot, let alone shoot from any distance without optics.
Still not convinced?
How many mule deer do you see in this pic?
Can you see the third deer?
If not, then I'll help you out.
I'll make it even easier to see.
If the first two hadn't jumped up and moved I probably never would have seen the third one.
Another good reason to use optics is low light conditions. When it the sun is down and the dark is approaching you often see game. It is similar in the morning before sunrise. Good optics that are correctly set up to fit you on your rifle are a great aid in low light shooting.
My camera had a hard time capturing these turkeys, but my scope did not.
Probably The Hermit and I will have to disagree on this, but having an open meadow 150 yards wide surrounded by heavy cover is an argument FOR optics, not a reason to avoid them.
Poor quality optics are a problem and should be avoided. Having your scope mounted on your rifle so that you have to fight it rather than having it work for you is a problem and should be cured. Backup irons are a very good idea on firearms used for serious purposes.
However, none of that changes the fact that good optics suited for the task at hand and properly mounted on your rifle will help you. Good optics on your rifle are like good binoculars. If properly used they let you see better in lower light and they won't slow you down. As it gets darker they will often let you shoot quicker because you don't have to spend time figuring out what is a shadow and what is your front sight.
3 hours ago