Trijicon MRO Advice

[jk_nh]

Looking to transition from a Cmore to MRO on my GMR15.  Question for the group:  which height mount would you recommend:  full co-witness or lower 1/3rd?

grateful for any advice. 

 

[Neomet]

I like full FWIW, but it really is a matter of personal preference.

 

[HoMiE]

Full, also makes transition to iron sight rifle easier. 

[mpeltier]

Another vote for full Co-witness.

[jkrispies]

The real answer should be "It depends on the size of your head" with a little bit of "they're pretty close to each other either way" and ending with "I bet it depends on the mount/sight combo."  In other words, if you're a smaller guy, absolute co-witness would be the way to go.  If you're a big guy, 1/3rd would be the way to go.  If you're "just right" then you could probably get away with either height.  Regarding the last quote, see my last paragraph.

 

Yesterday I shot a Steel Challenge match doing one set of strings with a dot at 1/3rd on a QR mount, then immediately removed it and shot irons (which are at full co-witness for the new kids reading this, LOL) on the same gun, and my times with the irons absolutely destroyed my dot times, which should not have been the case at all.  On this particular day, I was 10 seconds faster with the irons, when it should have been reversed (as in, my Optics time should have been 20 seconds faster than the time I presented) if I'd used my usual PCCO upper setup.  There was more going on than just sight height (for instance I had some ejection problems when I had the dot on the gun but never with the irons for some reason, I'm out of practice so my runs with the optic were basically practice runs before the irons, and a non-ideal dot that's designed more for tactical purposes than competition, etc.) but it's possible that mounting up at full cowitness gave me a better cheek weld which aided the gun in several respects... perhaps even in more consistent ejection.  

 

This is something that I'm planning to explore.  For instance, I believe my usual PCCO dot setup is a 1/3rd.... but now I'm not so sure. I'm going to put the dot I used yesterday on my usual gun and actually compare the heights by looking through them both at the same time.  By this same token, I'm going to guess that when a manufacturer advertises sight height to be "absolute co-witness" then it is probably following a standard mil-spec height standard, and their measurements are on or very close to so.  However, "1/3rd co-witness" sounds to me kinda like marketing speak, and many mount designers may well just be looking through their products and going "Yeah, that looks pretty good!" versus using an actual measured height that is standard across all combos.  For instance, a window size for one dot (say a Leupold DeltaPoint Pro) is different from a window size for a different dot (such as a Burris FastFire III), so how exactly are people justifying "bottom 1/3rd of the window" as a standardized measurement?  Just thinking outloud...

 

EDIT TO ADD:  I just tested the two mounts, one in front of the other and both on at the same time, and they're both 1/3rd cowitness, very close to each other in height.  One was a C-More RTS2 and the other a Trijicon RMR, both having very different sized and shaped windows.  One dot was SLIGHTLY higher than the other, but they were so close I'd be willing to say that the difference may have been due to different zero distances.  At least in the case of these two mount/sight combos, there's a decent indication that "1/3rd co-witness" may relate to an actual measurement.

Edited April 15, 2018 by jkrispies

[Pewpewlife]

I use the Battle Arms 1/3 mount. No complaints!