Folding sights and red dot mount

[tb-av]

Are all folding sights engineered the same with respect to height over mounting position?

I'm saving for a red dot and like the looks of the Larue 771 mount. How do you know where any given set of sights will align with respect to co-witness.

For instance would the 771 mount allow for say lower 1/3 co-witness with sights from several manufactures or are they all a bit different?

If different, how do you figure where things will align before you buy?

Thanks,

TB

[Quentin]

Before worrying about the optic - Most folding sights are the proper milspec height for M16A4/M4 rails. But some are commercial height and you can get a mismatch that won't zero properly. And of course if you put the wrong front sight on a railed gas block it can be way too short...

If your BUIS are proper height then you can usually get most RDS to cowitness somehow even if it's absolute instead of 1/3. A 1/2" riser ususually will raise the RDS from absolute to 1/3 cowitness.

I haven't used the Larue 771 mount but surely someone else will chime in soon. Which RDS are you expecting to get?

[tb-av]

I guess that would have been a good thing to mention as well.

The Aimpoint H-1

What I really want to do, aside from the AR mount, and the reason I am looking to the Larue is this.

I also have a High Standard .22 with a cheap red dot. Everyone seems to say the Larue will return to zero when you mount/dismount. So I was going to try to get double duty out of it. another reason I like that 771 for the streamlined post.

So that QD setup is an important thing for me.

[ucrt]

I've never noticed AR Folding Rear Sights that are different heights.

The Folding Front Sights differ. They come in two "rail heights".

#1 - Where the Handguard's rail and/or the Gas Block's rail are the same height as the Upper's rail (where the Rear Sight is mounted). A straight edge can be used to see if the Gas Block is the same height as the Upper's rail. They are starting to make Gas Blocks that are taller now but generally, these sights were made to put on a FF Handguard.

#2 - The Gas Block is lower than Upper's rail by soemthing like 1/2" -3/4". Again, you can use a straight edge to see if the Gas Block's rail is lower that the Upper's rail.

Now, there are other Folding Sights but they are not AR sights. Just stick with the quality names (Troy, MI, Magpul, etc.) and you should be fine.

Call their CS if you're still in doubt. Same with the RDS mounts, call the mounts maker if you have any questions. Choices of co-witness are when the BUIS alignments are dead center of the RDS or they are aligned 1/3 up from the bottom of the RDS.

My American Defense Systems QD mount for my T-1 is amazingly repeatable, I've done tests and I am very impressed. But I would never remount and relyon a Sight on my HD/SD gun without shooting it first. I think one time you'll remount the Sight on your AR and then wake up the next day and say, "Hmmm! Did I reset my Sight back to my AR?" Not worth it to me...

I use the QD repeatabilty to get the Sight out of harms way when I clean my AR, which is seldom and then get me back to a quick sight-in. I've never had to adjust it after a remount BUT I'm not playing with the Windage & Elevation adjustments like you would have to do.

But maybe it's just me...

.

[tb-av]

I guess I'm really asking too much to be able to switch between those two. I forgot I would have to change the wind/elev each time too.

Oh well, at least I know what I need to look at now for the AR setup anyway.

Thanks for the replies.

Tom

[ra2bach]

just a quick question I've been pondering - is a QD mount necessary for a RDS? I say it is not...

if your RDS goes tango uniform you can sight with the BUIS with no adjustments other than flipping them up if they fold.

I am a fan of fixed sights so it's even easier - I need do nothing other than drop my head till I'm on the rear sight and carry on. am I missing anything?

[ucrt]

just a quick question I've been pondering - is a QD mount necessary for a RDS? I say it is not...

if your RDS goes tango uniform you can sight with the BUIS with no adjustments other than flipping them up if they fold.

I am a fan of fixed sights so it's even easier - I need do nothing other than drop my head till I'm on the rear sight and carry on. am I missing anything?

============================

I agree. IMO, as a basic RDS setup I think you're dead-on but if I used the factory standard thumbscrews, nuts, ot whatever come with the sight - I'd Loc-Tite them and that makes it a pain to remove.

I Loc-Tite everything but with a QD mount it has a lever lock so I don't have to fight Loc-Tite to remove the RDS. I Loc-Tite the mounting screws that hold the RDS to the QD mount, so to change the QD mount would be a pain. If I remove the RDS to clean the gun, try a scope to test ammo, let someone else try the RDS, etc., there is no hassle going back with the RDS.

As a mini-test a few months ago, I shot 5-shots at 50-yards, removed my RDS, tapped it a couple times on the wood bench, remounted it, shot 5-shots and repeated until I had 20-shots. That was 3 remounts and I ended up with a 20-shot 1.75" group.

To me, that is excellent repeatability but I very seldom remove my RDS, I just like having the option.

.

[ra2bach]

============================

I agree. IMO, as a basic RDS setup I think you're dead-on but if I used the factory standard thumbscrews, nuts, ot whatever come with the sight - I'd Loc-Tite them and that makes it a pain to remove.

I Loc-Tite everything but with a QD mount it has a lever lock so I don't have to fight Loc-Tite to remove the RDS. I Loc-Tite the mounting screws that hold the RDS to the QD mount, so to change the QD mount would be a pain. If I remove the RDS to clean the gun, try a scope to test ammo, let someone else try the RDS, etc., there is no hassle going back with the RDS.

As a mini-test a few months ago, I shot 5-shots at 50-yards, removed my RDS, tapped it a couple times on the wood bench, remounted it, shot 5-shots and repeated until I had 20-shots. That was 3 remounts and I ended up with a 20-shot 1.75" group.

To me, that is excellent repeatability but I very seldom remove my RDS, I just like having the option.

.

I agree with loctiting whichever attaching screws the non QD mount use once it has found a home on my gun/receiver. to me, the ability to remove the RDS to "try a scope to test ammo, let someone else try the RDS, etc.," is not worth the extra cost and loctite is no trouble to remove if I am so inclined. but I do see your point...