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drvsafe 05-15-2013 02:01 PM

I'm looking at buying a red dot or holo sight for my AR and I'm trying to understand the difference between absolute and lower 1/3 co-witness. Can anyone give me compelling reasons to want either of them and which is preferable for range and HD use?

AgentTikki 05-15-2013 03:47 PM

If you have a fixed front sight, I would highly recommend 1/3.

In all practicality there's not a huge difference. Its just two different ways to cowitness.

Jpyle 05-15-2013 03:59 PM

Only difference if cowitnessing with dot on is the need to reposition head to see sights with 1/3, if scope fails or dot is off there is no real difference. Either way I believe it is just whatever works best for you and whatever mount height gives you the best eye relief and cheek weld.

Quentin 05-15-2013 05:59 PM

I also prefer bottom third cowitnessing. It gets the irons low and out of the way for normal RDS use.

Planejain 05-15-2013 06:28 PM

I second what Quentin likes. Its there when you need it for a SHTF moment, but out of the way for everyday play shooting.

TekGreg 05-15-2013 07:42 PM

The only difference, as I understand it, is the riser. If you mount an optic directly to your top rail, it will typically be going right over your iron sights. Place the optic on a riser, and the iron site sight line appears in the lower third of the optic out of the way of the reticle. Either way, you can buy the ~$20 riser and try both ways to see what works best for you!

AgentTikki 05-15-2013 08:16 PM

1 Attachment(s)
I'm gonna add this to my primer......seems to come up constantly...

Written and produced by Dieselpower

drvsafe 05-16-2013 01:19 AM

Should it matter if I have magpul buis? They're flip up...

Jpyle 05-16-2013 02:09 AM


Originally Posted by drvsafe
Should it matter if I have magpul buis? They're flip up...

No, as long as the mount for the RDS places the MBUS in the proper position relative to the dot, I.e. the center of the lens or the lower 1/3.

Anna_Purna 05-16-2013 02:17 AM

Magpuls are nice, just dont shoot 3 magazines in a row as fast as you can if you have one on the front or it might do an impersonation of the wicked witch of the west at the end of the movie!

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