[Skunkabilly]

Other than .5 magnification (does it make that big of a difference?) what's the difference between these two?

[Andrew Wyatt]

the 3.5 has longer eye relief and is about six times bigger. it also has a goofy BAC reticle that's huge and orange.



the 4X32 is smaller, more compact and has the ladder type reticle, which is just as fast and more precise.

[Bartholomew Roberts]

The TA11 (3.5x35) has 2.4" to ideal eye relief vs. 1.4" (4x32). It has a 10mm exit pupil vs 8mm (4x32). It has a 5.5 degree field of view vs. a 7 degree field of view (4x32). It is also several inches longer (about 4 I believe) and 5oz. heavier than the 4x32.

All TA11s have the BAC reticle (a fiber-optic tube illuminates the reticle day or night). Most 4x32s have this reticle also; but the TA01 and TA01NSN do not. All of the BAC reticles are much less cluttered than the TA01 reticle and all of the 3.5x35 and 4x32 BAC reticles have a simple ranging ladder as well.

This thread has an excellent discussion of the various ACOG reticles complete with real world pictures of them:

http://www.ar15.com/forums/topic.html?b=3&f=18&t=158932

The reticle on the 3.5x35 is actually smaller than the 4x32 reticle since both use ranging ladders, the lower magnification means slightly smaller markings. You can see this in the thread I mentioned above.

[Zak Smith]

All the 3.5x models have BAC. There are models with the following BAC reticle shapes: donut, triangle, and chevron. The model numbers start with TA11 and have a modifier based on the BAC reticle shape (or calibrated for .308 vs. 223)

The 4x models are splits into two:

TA01- these have no BAC, but are illuminated.
TA31- these have BAC. Same reticle shape options as the TA11.

The TA11 has about 2.4" of eye relief. The TA31/TA01 has about 1.5". The longer eye relief of the TA11 should make the BAC feature for close fast shots faster than the TA31, but this is a personal preference and splitting hairs.

Some people say the 3.5x version is brighter.

-z

[daniel501]

"All the 3.5x models have BAC"

OK, this brings up a question I've had for some time now.

I know that BAC means Bindon Aiming Concept and I know it means you keep both eyes open, and there's quick acquisition of the dominant magnified image.

In a mechanical or optical sense, specifically what about the 3.5x model gives it the BAC vs. absence of BAC in the 4x model? Aside from the obvious, i.e. the slight difference in magnification.

Won't any relatively low magnification scope exhibit the same properties as a "BAC" scope?

Thanks!

[Zak Smith]

Take this with a grain of salt because I only have trigger time on the TA01. However, the 3Gun guys sponsored by Team Trijicon on BrianEnos.com have said, paraphrased: the longer eye relief of the 3.5X allows you to retain more peripheral vision for close range shots; whereas the 4x version feels more like your head is "sucked into" the scope.


Won't any relatively low magnification scope exhibit the same properties as a "BAC" scope?

Who says it won't ?! Trijicon's Compact ACOG line (1.5x - 3x) all have BAC also.

I think the key part of making BAC work is a bright high-contrast reticle in the center of the view. If you concentrate on looking past the scope, the dot/reticle will be superimposed on the scene, just like a OEG (occluded eye gunsight). The BAC-style sighting can even be done with both eyes open on conventional scopes, e.g. a 1.5-5X Leupold. What makes it kind of awkward is that the reticle (eg, a duplex) is large and visually complex.

-z