Micro vs full size red dots?

[PNW89]

Why go with the larger red dot? By larger red dots I mean something similar to the Aimpoint M4.

Would the larger RDS slow you down at all?

[RonnyRonin]

People using NODs worry about objective size even in RDSs.

Battery type often changes with optic size (one of the main draws of a compM4 for me personally)

If you are fine with cr2032 batteries and are only worried about daylight hours it is hard to beat a smaller sealed micro dot (like say a holosun 403R, or its sig/primary arms equivalent).

I got a used aimpoint compM2 for instance because it was much cheaper than a t1/h1; so price can be another boring answer to the question as well sometimes.

you'd be hard pressed to catch a difference between a large optic and a small one on a shot timer; but if you have to carry the gun for multiple days in the mountains shaving several ounces on an optic can pay off more than it looks on paper.

[Mr. E. Monkey]

I've used both--have a comp c3, L-3 MRDS, and a few other small RDS (Primary Arms for a few), though I find myself preferring prism optics over red dots these days.


I've never run any of them really hard, so I can't speak to durability, but the perceived durability was one of the main reasons I bought the Aimpoint.  That, and I had gotten used to using one similar to it.  Beyond that, though, I don't know of any real reason why I would choose one over a smaller dot, if I were to do it again.


I don't know if anyone else has had similar experience, but I think that it does feel, sometimes, like the bigger optic is easier to sight in on--being more "substantial," it feels like my eye is drawn to it more quickly, but that is probably just a training issue.  And I haven't run any timed drills to compare the sights to see if it makes a difference, but I'm betting that RonnyRonin is right that there likely isn't much real difference, it's probably more in my head.

[NT2C]

People using NODs worry about objective size even in RDSs.

Battery type often changes with optic size (one of the main draws of a compM4 for me personally)

If you are fine with cr2032 batteries and are only worried about daylight hours it is hard to beat a smaller sealed micro dot (like say a holosun 403R, or its sig/primary arms equivalent).

I got a used aimpoint compM2 for instance because it was much cheaper than a t1/h1; so price can be another boring answer to the question as well sometimes.

you'd be hard pressed to catch a difference between a large optic and a small one on a shot timer; but if you have to carry the gun for multiple days in the mountains shaving several ounces on an optic can pay off more than it looks on paper.

To which I'm going to add that the smaller the optic the less chance of it being smacked on something while moving.  I was walking around in the house last night after getting back from shopping and in our master bath there's a little "pony wall" between the sink and toilet.  Walking past that to put something on one of the bathroom shelves I caught the top of my Holosun 507K X2 that was on my holstered sidearm on the wood trim of that wall hard enough to leave a dent in the wood and hurt my hip.  The red dot seems fine, the dot still hits the same spot as the laser on my under barrel light so it doesn't seem to have hurt accuracy any, but boy did that rattle me when it happened.  If the RDS were larger I could see that happening more often going through doorways, etc.

[MacWa77ace]

30mm objective lens RDS vs 20mm RDS.

Light transmission usually. the larger the objective lens the 'brighter' everything appears thru the optic. But that also has to do with quality when comparing apples to apples, cheap 30mm vs High quality also makes a difference in light transmission and clarity.

Next would be field of view. Smaller objective lens means small FOV usually.


I have a 30mm RDS that uses a CR2032. IIRC my 20mm runs on the same battery type.
I have them mounted to the same height so I can use the same magnifier for each if I want. But the magnifier seems to work better on the 30mm because the 20mm seems to block some of the magnifier's field of view. Which of course is really only distracting to a degree. It doesn't effect the optic's actual field of view.

I've gone prismatic also. Which I have a 32mm 4x, 17mm 1x, and 16mm 1.5x. But I'd like to try the Trijicon MRO.

[RickOShea]

30mm objective lens RDS vs 20mm RDS.

Light transmission usually. the larger the objective lens the 'brighter' everything appears thru the optic. But that also has to do with quality when comparing apples to apples, cheap 30mm vs High quality also makes a difference in light transmission and clarity.

For an optic to have optimal light transmission, the exit pupil of the optic needs to be at least the same diameter as that of the pupil of the human eye. The pupil of a typical, healthy human eye has a diameter around 2mm in bright light, and around 7mm in low light.

To find the exit pupil of an optic, you take the diameter of the objective lens and divide it by the magnification power. So a 30mm divided by 1x would have an exit pupil of 30mm, and a 20mm divided by 1x would have an exit pupil of 20mm.

Since both the 30mm and 20mm exit pupils are well in excess of the 2mm to 7mm pupil diameter of the human eye, and with all other things being equal (lens quality, lens coating quality, number of lenses in the system, etc.,) any difference in light transmission between a 30mm red dot and a 20mm red dot would seem to be negligible....at least on paper. 

[RonnyRonin]

As rick says; the size of the optic will have zero effect on light transmission in the case of red dots during the day. Lens coatings and lens materials will have a *huge* effect on light transmission though; and oddly enough price doesn't track very directly onto clarity in my experience. HOWEVER; where it does matter is once again under NODs; my compM2 works far better than my micro aimpoint, and everyone says an eotech works even better. Lens coatings matter a LOT of course with NODs, but my two aimpoints are theoretically coated the same and just the amount of fuzziness from both the dot and housing means that the difference between 30mm and 20mm is actually meaningful on the green screen.

A larger window will allow for even sloppier head positioning when shooting fast or around weird obstacles, but even the smallest of red dots is so forgiving that its difficult to notice a difference. I've used both my compM2 and my various t1 clones in vtac drills and other weird contortion games and I would hesitate to say one was any better.

[PNW89]

Well the Sig Romeo 7 came in and I like it alot...time to pony up for the Aimpoint I think.

[PNW89]

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[RickOShea]

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Is that a PSA Mock Dissy upper?

[PNW89]

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Is that a PSA Mock Dissy upper?

Yep with a magpul rifle length handgaurd.

[RickOShea]

Is that a PSA Mock Dissy upper?

Yep with a magpul rifle length handgaurd.

Cool.

I picked-up a mid-length upper with an FN barrel from PSA a while back.

[PNW89]

Is that a PSA Mock Dissy upper?

Yep with a magpul rifle length handgaurd.

Cool.

I picked-up a mid-length upper with an FN barrel from PSA a while back.

PSA premium is all I goto anymore, thier budget guns seem to be the ones everyone knows but these rifles are solid. My PSA shoots better than my BCM with a lightweight barrel. Toolcraft BCGS and CHF FN barrels for $420 can't really be beat or not anywhere I have seen.