I need some help understanding optics theory

[the_horak]

I'm new to this forum but I've been searching it and using it for a little while now. I just never made an account til now. I'm much more beginner than most everyone here. I shot bb's as a kid and somehow (thankfully) got back into it at 35 haha. I've got a CO2 Umarex pistol and my Gamo break barrel should be here today. That's my setup and I don't plan on changing it much for a little while.

The Gamo is scope only with no sights built in. I like the reflex sights as a closer range option at 10 yards or so. But I don't understand well enough. Optics are there to compensate for drift or fall as the pellet flies correct? All things being constant, I would just calibrate the optics to point to where the pellet will hit. So why is leveling and precision mounting so important? Wouldn't calibrating the optics take that into account?
Also, the reflex sights are often talked about as mounted offset on semiautomatic rifles. So I see a lot about how the shooter tilts the rifle to switch from scope to sights. I understand that this is to keep the rifle in its optimal position. Me using a break barrel, I need to lose that position with every shot anyway. So can I hold the rifle in the normal upright position and use the sight at its angled position? I would just adjust it to point where the pellet will hit, right?
There's gotta be stuff that I don't know or understand, but this is where I am so far. From what I know or don't know, I don't understand why certain things need to be done when the optics need to be dialed in anyway.

 

[Gerry52]

Leveling & precision mounting of optics takes the fallible human element out of the equation (in theory). It's essential for REPEATABLE accuracy. Yeah you can move the crosshairs to wherever your pellets hit BUT can you GUARANTEE your body will be holding gun at exactly the same position & attitude on every shot? True Leveling of scope on horizontal & vertical axis & a level on scope to help eliminate cant of your gun (vertical tilting left or right) is about repeatable & DEPENDABLE results at different ranges. No human body can do this as well as a precision optic that's setup correctly.

 

[the_horak]

Yeah you can move the crosshairs to wherever your pellets hit BUT can you GUARANTEE your body will be holding gun at exactly the same position & attitude on every shot?

Thank you for the reply, it is helpful. But can't this be said with the optics precisely installed as well? Or is there something related to a properly mounted optic that helps alleviate the human error? What would that be? Again, thank you.

 

[GeneT]

The fundamental reason to get your optics aligned correctly is to be able to make accurate adjustments. If your optic is canted a bit, you can still zero it for a specific distance, but if you decide you want to adjust you impact an inch higher (for longer range or because you like to hold low on the target so you can see it better) then that's a simple elevation adjustment on a well mounted optic. If your optic is canted, with respect to the barrel / gravity, you will need to also apply some windage to compensate for the cant, greatly complicating the adjustment.

GsT

 

[the_horak]

@GeneT Okay, that makes sense and it helps me better understand @Gerry52 . If I am raising or lowering the barrel, the canted scope's point of view is that I am adjusting X & Y axis. In theory, zeroing in a canted optic for exactly one specific shot from a completely constant point can be reliable, but once you use it for any other target, it is much less reliable and predictable. Yes?

 

[Gerry52]

Thank you for the reply, it is helpful. But can't this be said with the optics precisely installed as well? Or is there something related to a properly mounted optic that helps alleviate the human error? What would that be? Again, thank you.

That's what I was trying to explain. An optic locked into position will maintain where one sets it up & locks it in. A human body, not so much. Maybe I'm not understanding what you're looking for. We work on technique with our guns to train our bodies & program muscle memory but we'll never be as precise as a scope locked into place for REPEATABLE, DEPENDABLE results.

 

[the_horak]

That's what I was trying to explain. An optic locked into position will maintain where one sets it up & locks it in. A human body, not so much. Maybe I'm not understanding what you're looking for. We work on technique with our guns to train our bodies & program muscle memory but we'll never be as precise as a scope locked into place for REPEATABLE, DEPENDABLE results.

No, I get it now.

 

[JimD]

It may also help to visualize an imaginary straight line through the center of the optic and a slightly downward slightly curved line starting with the bore of the rifle. When we zero the scope we are aligning the line through the scope with the line through the bore. Because the scope is above the bore they start out that way and the scope has to be tilted down for the sight in. In reality the lines will cross twice if you are sighted in right but if you do it like I do and have the zero distance be about at the apex of the pellet path the two points are as a practical point on top of each other - indistinguishable. But you could have an initial cross over point at like 15 yards, then a pellet path above the line through the scope, and then the two lines crossing at like 35 or 40 yards. We normally call the second cross over point the sight in distance. My higher powered airguns are sighted in at 30 yards and I essentially never have to hold under the target. I always can hold on or above the target. If I zero'd for 35 or 40 yards then the pellet impact would be noticably above the aim point at 25 and 30 yards. This isn't a right and wrong thing, it is a choice of how you want to adjust things.

Some like to install a red dot on the side of a gun and use it for very short range. On my bullpups the scope is so high I have to hold over my target by like 2 inches at short range. That is the kind of shot where some want to use another sighting system. I just hold high.

 

[cahil_2]

I don’t know if reflex dot sights are springer friendly. I put one on my springer and it lasted 3 shots.

 

[Elgreco]

Hey Horak, as far as the why for leveling the scope Gene t covered it.
It seems u dont have a good understanding for the use of the red dot in conjiction with a scope. It has nothing to do with the rifle being in the optimal position.
It has to do with with tactical operators and the nature of their job. They would use the scope for taking longer shots ( imagine for example a souldier approaching an enemy site such as appartment buildings and wanting to take a wimdow shot from distance) and then using the red dot for close quarters fight ( as clearing rooms). Mounting a red dot on a picatiny on top of the scope is an option but makes the rifle top heavy and cumbersome.
U can mount a quality red dot alone or in conjuction with a magnifier on a pcp or a springer. I have had my vortex solar red dot and a 3x magnifier on various springers, including an ASP20 ( magnum springer) with no issues.

 

[DesertSilver]

Hey Horak, as far as the why for leveling the scope Gene t covered it.
It seems u dont have a good understanding for the use of the red dot in conjiction with a scope. It has nothing to do with the rifle being in the optimal position.
It has to do with with tactical operators and the nature of their job. They would use the scope for taking longer shots ( imagine for example a souldier approaching an enemy site such as appartment buildings and wanting to take a wimdow shot from distance) and then using the red dot for close quarters fight ( as clearing rooms). Mounting a red dot on a picatiny on top of the scope is an option but makes the rifle top heavy and cumbersome.
U can mount a quality red dot alone or in conjuction with a magnifier on a pcp or a springer. I have had my vortex solar red dot and a 3x magnifier on various springers, including an ASP20 ( magnum springer) with no issues.

But the red dot needs to be quality red dot or it might fail in a short time.

 

[the_horak]

It seems u dont have a good understanding for the use of the red dot in conjiction with a scope.

I don't doubt that haha. If I ever decide to use the reflex because I wanna scope for longer range, we'll see. But, the theory of sighting the reflex sights and the scopes are the same right? They need to be sighted while leveled and straight above the barrel. That's why people tilt their rifles with offset reflex. You can't sight an offset when the reflex isn't level.