Fixed sights and Red dots

[breakingtime91]

I have seen a few people post that they run a fixed front and fix rear when running a Red dot with a 1/3 cowitness mount. I understand having a fixed front in case the optic fails you can "ghost ring" it but why the fixed rear? I run my troy foldable front up but my rear down but am putting together my second carbine and am wondering if there is something I don't know.

[BehindBlueI's]

I have seen a few people post that they run a fixed front and fix rear when running a Red dot with a 1/3 cowitness mount. I understand having a fixed front in case the optic fails you can "ghost ring" it but why the fixed rear? I run my troy foldable front up but my rear down but am putting together my second carbine and am wondering if there is something I don't know.

I have used a fixed rear because the M16 carry handle didn't offer another option. With lower 1/3, I never noticed them but could transition instantly if needed.

[txdpd]

I've found that ghost ringing a lower third sight with a carbine length front sight translates to 9-12" high at 10 yards. It just gets sloppy and slow trying to compensate for extra sight height.

[BillSWPA]

I have used a fixed rear because the M16 carry handle didn't offer another option. With lower 1/3, I never noticed them but could transition instantly if needed.

This is how I look at it as well. Optics can fail, and the foxed front and rear with lower 1/3 co-witness provides the fastest backup option. Just slightly drop the head, and you are back in business.

[breakingtime91]

Do you guys zero the irons through the red dot?

[txdpd]

Do you guys zero the irons through the red dot?

I zero independently and then get a good look at the dot through the irons. Then I have a mental reference to where my red dot should be in relationship to the irons. It was a big deal when I had an eotech, never had an issue with the Aimpoint.

[BehindBlueI's]

Do you guys zero the irons through the red dot?

My steps are:

1) Zero irons
2) Attach RDS
3) Get approximate zero on RDS based on irons
4) Clean up RDS zero
5) Verify irons zero

[Luke]

Do you guys zero the irons through the red dot?

I wanna say GJM experimented with this and notes there is a ever so slight POI difference between sighting in through the glass and without it. Hopefully he will chime in.

[SamuelBLong]

There is a parallax shift when zeroing irons through the optic and then removing the optic to shoot.

Two ways to avoid the issue:

1) Zero the irons, add the dot and then zero the dot. If the dot fails, remove the optic, flip up irons and keep going.

2) install your rear iron sight in front of the optic and zero the irons looking through the optic.

There may be some slight parallax shift with #2 if you end up removing the optic and shooting irons, but way less than if you're shooting irons with the RDS optical glass between your front and rear iron sights.


I solved the issue by using a durable purpose built laser as the secondary sighting system... Dot goes down, activate the laser and see the laser dot through the optic glass.

For the record I zero irons and optics independently, and use a parallel zero on the DBAL / PEQ-15.

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[HCM]

My steps are:

1) Zero irons
2) Attach RDS
3) Get approximate zero on RDS based on irons
4) Clean up RDS zero
5) Verify irons zero

This^^^

POI shift will vary with the optic. Some optics have a bit of fish eye or slight magnification.

[Maple Syrup Actual]

I can tell you exactly why I use a fixed rear behind a Micro...the sights I have on that rifle came as a pair.

Although I actually use an absolute cowitness, not a lower third, because I find that on Micros, the emitter protrudes into the large ring on Troy rears. So I just use an absolute and look a little over the sights and it doesn't bother me at all.

[Robinson]

Timely thread, as I'm considering what optical sight I want to install on my rifle. It currently has Troy fixed irons installed and I like them. I am thinking about purchasing a red dot sight and am wondering whether I will be better off with a true cowitness or a lower third cowitness. Can anyone having experience with both setups offer additional insight as to the pros/cons of each?

Plus, am I right in assuming you achieve one or the other based on the type of mount used?

[SamuelBLong]

Timely thread, as I'm considering what optical sight I want to install on my rifle. It currently has Troy fixed irons installed and I like them. I am thinking about purchasing a red dot sight and am wondering whether I will be better off with a true cowitness or a lower third cowitness. Can anyone having experience with both setups offer additional insight as to the pros/cons of each?

Plus, am I right in assuming you achieve one or the other based on the type of mount used?

Yes it's based on the mount.

Lower 1/3rd provides a cleaner view of the target because your irons, lasers and lights are in the bottom of the window, and your head can be positioned slightly higher which reduces fatigue.

Absolute provides greater consistency between irons and shooting the dot by forcing your head into the same spot every time. You will lose a large portion of the target view if you have anything mounted at the 12 o'clock position down at the end of the rail.

It really comes down to how your brain works... If you're ok with the dot floating in space above any fsp, go lower 1/3. If you're OCD like me and have to have everything line up and be consistent across the board, go absolute.


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[Lex Luthier]

Yes it's based on the mount.

Lower 1/3rd provides a cleaner view of the target because your irons, lasers and lights are in the bottom of the window, and your head can be positioned slightly higher which reduces fatigue.

Absolute provides greater consistency between irons and shooting the dot by forcing your head into the same spot every time. You will lose a large portion of the target view if you have anything mounted at the 12 o'clock position down at the end of the rail.

It really comes down to how your brain works... If you're ok with the dot floating in space above any fsp, go lower 1/3. If you're OCD like me and have to have everything line up and be consistent across the board, go absolute.


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Thanks for such a clear concise answer. I too am looking at getting a carbine set up later this summer, and this helps.

[Dagga Boy]

I wanna say GJM experimented with this and notes there is a ever so slight POI difference between sighting in through the glass and without it. Hopefully he will chime in.

This is only an issue with the T2/H2's due to the optimization of the lenses for optics to be mounted behind them. With my Aimpoint PRO Staff hat on....here is what I recommend. Zero the irons and red dot through the glass as you are not likely to be taking the sight off the gun if for some reason the sight is not on and you need to go irons. If you have a need to be removing the Micro regularly, then obviously just zero the irons and be okay with them being a little off.

Setting the gun up...for me personally with a long background with these in the LE environment, with a fixed front I like either the factory Aimpoint or a lower third mount. For fold downs, I run absolute. For a front only (I have an AUG done like this), I also run absolute so it works like a gigantic ghost ring.

Also, I like some of the offset iron set ups as well for their actual role as a rapid back up.

[spinmove_]

I'm sure this will vary from optic to optic, but approximately how much "off" are we talking about if you zero your irons prior to adding the optic and then go to shoot with the irons through the optic?

[texasaggie2005]

I'm sure this will vary from optic to optic, but approximately how much "off" are we talking about if you zero your irons prior to adding the optic and then go to shoot with the irons through the optic?

With my T2, I was about 1/2" right at 25yds.

[spinmove_]

With my T2, I was about 1/2" right at 25yds.

Wow, so looking at up to or beyond 2 MOA in any given direction.

I guess the next question is this: is it better to zero through the optic and bet that you won't have to remove it should a malfunction occur or is it better to zero independent of the optic and immediately remove the optic should a malfunction occur?

I'm sure that's dependent of what kind of optic you're running and how durable it is and how likely it is for the housing/glass to break, but it's definitely something to consider.

[BWT]

I use a 1/3rd Co-Witness on my AR's.

I debated keeping the rear sight deployed/folded before getting an AR. However, after purchasing one I didn't appreciate shooting an AR left handed (without an ambi-charging handle) meant manipulating the charging handle by hooking my right index finger over the rear of the receiver and relying on my middle and index finger to pull the charging handle.

Candidly, I pretty much either have to run the rear sight deployed, go to an ambi-charging handle (I'm happy with the way it works), or re-visit this configuration to find a workable solution via trial and error.

Since I paid $120 for a folding Troy rear on my Midlength and never folded it because of the aforementioned conditions. I decided to save $60 and go with a fixed rear by Troy on my second AR. I feel that the shape of rear sights for DD and other rear sights will probably obstruct my hand from manipulating the charging handle the way I have been. So, I've stuck with Troy.

God Bless,

Brandon

[shane45]

For larger aimpoints I like lower 1/3. For smaller ones like the micro, I like absolute. With larger aimpoints, I like a fixed rear. If the dot should have an issue I can easily transition to irons without taking my eyes off the target. But as my eyes aged I have heavily migrated over to variable optics that have daytime usable red dots and a 1x setting.

[Digiroc]

9345

My Sig is setup to co-witness in the lower third of my red dot. The sights fold down and I leave the front sight up and the rear folded. The red dot appears right on top of the front sight post. The Sig also has a LaserMaster and all three line up at 25 yards with the laser just under the red dot. Since the red dot is on top and the laser on the rail below this seems about right to me.

With the red dot off (or inoperable) the front can be ghost ringed using the optic, or I can flip up the rear sight and get a good sight picture through the lower third of the optic. I also have a streamlight on a short rail on the left side.

9346

Another rail on the forearm allows the Sig to be mounted on any one of my Manfrotto tripods with a Pickatinny to camera mount adaptor I built. The tripod has a hydraulic ball head that can be finely adjusted to hold the weapon rock solid, or released just enough to allow movement of the weapon for precision aiming yet holding it's position when released. A Really Right Stuff™ quick release clamp releases the weapon in an instant for offhand use.

Digiroc