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Old 10-11-2017, 6:21 PM
phreaticus phreaticus is offline
Join Date: Nov 2015
Location: Mountain View, CA
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In case this thread is still of interest for like minded folks...

Personally, I subscribe to the "purist" philosophy on pistol red dots - key benefit & design thesis of red dot concept is to be 100% threat/target focused; irons are relegated to emergency backup only. This is how we've been using red dots on rifles for years...

So, on the quest for most uncluttered RMR window as possible, while still having a useful iron backup setup in case the optic/battery fails, it's been suggested by some sources that one can run a suppressor iron sight up front, and simply remove the rear iron sight altogether. In case of red dot failure, one simply centers front site within the RMR frame and it's claimed that one can shoot fairly accurately this way.

So, I finally got around to trying this setup today. Glock 17 with RM06 and Trijicon suppressor front iron night sight only (removed Trijicon suppressor rear iron sight, which previously gave me a lower 1/3 cowitness).

Results were a very clear win - without the rear iron sight, the RMR optic sight picture is much cleaner, making initial acquisition of the dot on draw/presentation & under rapid fire - much easier. I think this clean FOV is why some folks prefer the Delta Points over RMRs...

As for how this setup performs for point shooting with no red dot - also a win. I did some timed drills with red dot on/off, using only a front sight centered within the RMR housing/frame. Results:

- 7 yd slow aimed fire: 2 group, POA/POA. Vs 1 group with RMR dot on
- 7 yd Bill drill: 8 groups, POI 2-3 left, in times that are normal for me (~ 3.5-4 sec from concealment). Vs 6 groups POI/POA with RMR dot on
- 10 yd slow aimed fire: 3 group, POA about 2 high left. Vs 2 group POI/POA with RMR dot on

Those numbers work just fine for me, so this is my new setup


Originally Posted by phreaticus View Post
Not sure if this is useful to anyone, but here is some more info I've managed to glean w/regard to co-witnessing sights with RMR on Glock 17/19/34:

Some standard sizing refs
- G17/19 standard OEM rear sight: .256, front: .165
- Bottom of G17/19 dovetail slot to top of slide: .075
- Height of Trijicon RMR (from bottom of Glock 17 rear dovetail sight slot to top of RMR base, where irons must look over): .305
- Height of Trijicon RMR base, over top of slide: .230
- Typical rear sight notch depths: .090-.120"

Tall sights for RMR setups:
(Note, these are full measurement from bottom of G17/19 dovetail slot to top edge of sight)

Absolute co-witness sizes:
- Ameriglo: .500" rear, .407" front
- Dawson: .495" rear, .485T front

Lower 1/3 co-witness iron sizes:
- Trijicon suppressor: .361" rear, .365 front
- Ameriglo: .394" rear, .315" front
- Dawson .395" rear, .390" front
- 10-8: .395 rear, .315 front

Obviously, there are others, but these are very popular ones with published specs.

@ Powder_Keg: I'm currently running a G17 with blacked out Trijicon suppressors 361/365 combo on G17 in lower 1/3 cw, which I think will be pretty similar to your G34 Ameriglo setup from ATEI. Enjoy it, and be sure to let us know how you're getting on.

For what it's worth, I recently shot an instructor buddy's G19 Leupold Deltapoint Pro which he has setup with the DPP adjustable rear iron sight module. It was adjusted so the rear iron was just barely visible above the red dot mount (much lower than a lower 1/3 co-witness, but still useable for backup). The uncluttered FOV and clarity of glass was way more comfortable than my RMR setup. I'd like to mimic that approach with my G17/RMR setup, if I can find a .330 ish rear sight... To be honest, I think G19 + DPP will be my next experiment...

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