Why isn't a red dot sight lower?

[JG007]

I was just holding my AR and thinking a lower than cowitness mount might feel right, then thinking about why the mount is there.

Is it for an actual efficiency/ergonomic benefit?


Or was it simply based on accommodating the fixed front sight? And is the taller 1/3 mount also just to accommodate the ffs? Having a periscope setup seems counterintuitive compared to normal sights.

Then you'd think the ffs could have been made lower originally, but was it made that height to accommodate the carry handle which couldn't be any lower?

I'm just a low speed guy thinking out loud and there are some very knowledgeable guys here.

There's probably a good reason for me not to buy a lower than cowitness mount and micro buis

[Airhasz]

The stock, buffer tube and barrel are on the same plane, that puts your eyes above the barrel.

[JG007]

But why not half an inch instead of an inch and a half

[Clint]

Its related to the distance from the cheek to the eye.

With a traditional drop style stock and action, the natural line of sight is just above the bore.

With the AR inline design, the natural line of sight is approximately 1.6" above the bore.

[ggammell]

But why not half an inch instead of an inch and a half

Cheek weld. Unless your eye is only half an inch above your weld...

[JG007]

That makes sense, but it does make risers seem more redundant on AR's

[Iraqgunz]

Please visit the Optics and Mounts area.

https://www.m4carbine.net/forumdisplay.php?13-Optics-amp-Mounts

[Singlestack Wonder]

But why not half an inch instead of an inch and a half

Stoner built carefully thought out ballistics into the sight design. For example a 100 meter zero allows the sights to be placed on the center of a target anywhere from 5 meters to 200 meters and be guaranteed a hit +/- a couple of inches from the POA.

[turnburglar]

Because you can't cram your face anymore into the buffer tube. I have 'tried' to use an optic lower than cowitness (tried zeroing a buddies rifle who bought the wrong mount) it was impossible and not comfortable in any sense of the word.

The only reason other rifles can mount optics lower is because their bore isn't inline with the stock like on the AR.

[JG007]

Because you can't cram your face anymore into the buffer tube. I have 'tried' to use an optic lower than cowitness (tried zeroing a buddies rifle who bought the wrong mount) it was impossible and not comfortable in any sense of the word.

The only reason other rifles can mount optics lower is because their bore isn't inline with the stock like on the AR.


thanks, that makes sense, I was getting down on my AR with cowitnessed micro and it did appear I could get down on the stock low enough to make the dot disappear, but that's not something im ready to gamble on

[Blastem]

I have also noticed that having the sights higher rather than lower can reduce the amont of mirage caused by a hot barrel and helps me see the target better.

[wolf_walker]

I was just thinking about this the other day playing with a new RDS, it's lower 1/3.
I've had absolute in the past, which I prefer, but honestly even the irons are higher
than I'd like. My cheekbone is overly high and my face is not well padded. The
recoil and such is so mild on the AR it's not that big a deal, but it isn't ideal having my
teeth on my stock basically instead of my jawbone. It's not that unusual a problem
really, there have been stock risers of one sort or another for as long as there have
been long guns.

[titsonritz]

I have also noticed that having the sights higher rather than lower can reduce the amont of mirage caused by a hot barrel and helps me see the target better.
This is why modern fighting rifles (post WWII) have sights well above the bore axis, it was noticed high volumes fire created heat mirage and disrupted the sight picture. Look at any rifle out there, AR, AK, G3, FAL, Galil all have their sights well the barrel.

[gsh341]

With any optic there are limitations concerning height over bore.

First, how much height is caused by mounting requirements?

With a red dot, the package is fairly compact, but the dot will be about centered in the sight, so you're looking at some height there. Plus, how does the sight mount to the rifle? A rail will add some height where attaching directly to the receiver can be a bit lower. If you're using a scope, the objective lens will only allow it to be mounted so close to the rifle before it runs in to the barrel or receiver.

Second, how does your face shape line up your eye to the rifle?

Your face will only allow your eye so close to the stock. If your cheek is solidly against the stock and the sight is too low, you'll have to mount the optic higher so you can see through it. However, if the optic is as low as it can get and your eye is below the sight bore, you'll need a riser for your cheek so you can get a solid cheek weld and still see through the scope. On an AR, you have a stock that is inline with the barrel where on a traditional bolt action rifle, it typically drops. Both will need different things to fit your face properly.

As far as trying to get the optic low for accuracy, its not really an issue. Most optics will keep you within 1.8" of the barrel and that is close enough that only on shots under 10 yards or so will it really become something to worry about.

Here are a couple articles that cover this topic.

http://www.longrangehunting.com/articles/fitting-long-range-rifle-1.php

http://unionsportsmen.org/stock-fit-is-important-for-rifles-too/

[Tape]

I have a 3/8" mount and until you try it you would know why you use a higher mount

http://tse1.mm.bing.net/th?&id=OIP.M75f611dbca81d656eef2415c4e6ffd41o0&w=300&h=200&c=0&pid=1.9&rs=0&p=0&r=0


I now have a GG&G 1" mount and it's so much better. The main reason is comfort, trying to squeeze you neck down on a low mount red dot is so uncomfortable and not a natural aiming position. I wondered myself is why I have the 3/8 mount hanging on the corkboard.:)

[trinydex]

you would have to ask: what's benefit of having the sight lower? the most common answer will be height over bore. however, height over bore issues are most pronounced with the 1.5" height when addressing very very close distance shooting. in my experience it is only relevant within 7 yards, even at 10 yards, with a 100 yard poi poa intersection, the height over bore is not significant enough to affect head shots.

there are some benefits to having the sight higher. fat faces. shouldering a rifle with lots of chest-borne gear where perfect stock placement and perfect cheek weld is inhibited. gas masks and other protective equipment that is worn on the face. accommodating sight over designating devices like lasers, flashlights, and anything else that might be incidentally mounted on the 12 o clock rail. being able to mount optics in front of primary optics like clip on infrared and night vision devices (these are too large to mount lower). etc etc etc.