New to the AR world.

Yes, your normal average rear flip up sight should match as long as everything is basic/normal/common/spec.

The flip up sight heights mimic the old school A2 front sight dimensions.

I use Magpul plastic rear flip ups normally because they are good value for money. I've gone cheaper and gotten junk.

To note: if you plan on irons only, then there are better options than flip ups

The point of flipping is so they are a backup and out of the way.

The front sight is still going to be in the picture, but you'll soon ignore it, unless you're looking for it. I have a couple of AR's set up like yours with a red dot on them and it works fine. I use the Magpul rear sight as a back up sight too.

When you add a red dot, use what is called a “One third lower co-witness” mount.

When looking through the red dot, the front sight will be down in the lower one third part of the window when the red dot is in the center.

Then, when using the iron sights, the red dot and the iron sights will align with each other in the lower one third of the window.

The lower one third co-witness is the best compromise giving you the least cluttered view when using the red dot alone while retaining the ability to see the iron sights through the red dot.

I used the plastic MagPul rear sight while saving up for an Aimpoint micro. They’re ok strictly as a back up sight, but don’t hold zero very well. Metal rear sights are much better.

I never did get used to having a blurred image of the front sight in my optics image so I made it go away. Have pop up sights on 45 degree mounts so I can just roll the rifle & use them if need be-works for me.

The Magpul MBUS rear sights are pretty good. I’ve shot with them out to 200 yards and let’s just say the sights aren’t the limiting factor there.

I’ve never tried this but it’s fairly common for people to co-witness their irons sights with their red dots meaning they intentionally have the iron sight visible through the red dot and sighted in with it at the same point. This is in case the battery dies or the dot otherwise fails. They can virtually instantly transition to the iron sights.

If you plan to practice with the iron sights and red dot, there are replacement front posts that mimic red dot use. They have a bead on top of the post and you cover the target with the bead just like you would with the dot. Again I have not tried this but it’s out there.

One of my PSA rifles has a carry handle sight. Unless you already plan to put a red dot on it, maybe try the carry handle. I prefer mine over a scope for shooting enjoyment. Accuracy is very good and they are surprisingly sophisticated. Then again, if I know I have to get the desired result, I’d use an optic. Red dots and my eyes don’t agree but some sort of optic is easier to use and faster to learn. I spent the better part of a year trying different things for my PSA before I settled on it’s current set up.

I don't care for magpul flipups or any other type that are spring loaded in the "up" position. You can also cut down your detachable carry handle like below to lighten it up- you will still have a good adjustable sight and be able to mount a RDS on the expose forward portion of the rail to co-witness.

Oldschool shooter said:

I have a PSA AR-15. The front sight is the type mounted in an A-Frame as part of the gas block. It did not come with a rear sight. Would any flip up tear sight be tall enough, or do I need a special rear sight ? I do have an old school removable carry handle with the 2 leaf rear sight, but was looking for something a bit lighter.

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With the removable carry handle, the rear sight sits slightly higher than with the original non-removable carry handle. To match the removable carry handle sight (or any modern flip-up rear sight, really), you need a front sight tower (base) that has a small "F" marking. (It's slightly taller than the original tower.) The first thing to do is check if you have an "F" marked front sight tower. If it's a recently-made gun, chances are you have it.

Regarding flip-up rear sights, FWIW the Army uses the one made by MA Tech. I suppose that's as good as any.

Keep in mind that if you cut off the front post, it is very difficult to replace with another GI-style front sight base if you ever want to go back to that configuration. The new ones are not drilled for the mounting pins and it is nearly impossible for a home smith to drill new holes which will match the grooves in the barrel exactly.

If there is any possibility you will want to go back to a GI front sight at some point, knock out the pins, remove the front sight base, and replace it with a railed base or one with an integrally mounted flip up sight.

NIGHTLORD40K said:

Keep in mind that if you cut off the front post, it is very difficult to replace with another GI-style front sight base if you ever want to go back to that configuration. The new ones are not drilled for the mounting pins and it is nearly impossible for a home smith to drill new holes which will match the grooves in the barrel exactly.

If there is any possibility you will want to go back to a GI front sight at some point, knock out the pins, remove the front sight base, and replace it with a railed base or one with an integrally mounted flip up sight.

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Good advice. The original design, attaching the front sight tower to the barrel with tapered pins, is still IMO the best method. But now, bases are made that either clamp on, or are held to the barrel with set screws. You just about have to go with one of those if you are doing a replacement.

I'm partial to the A.R.M.S. folding front sight base (clamp-on). It keeps the GI profile, but folds down out of the way when not needed. Kind of pricey, though.
http://armsmounts.com/shop/iron-sights/a-r-m-s-41-b-silhouette/

Oldschool shooter said:

Not looking to change the front sight, only looking at rear sight options.

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Right on.
I use the Magpul polymer flip ups and they are good for the money. Ive never noticed an issue with them losing zero, but then they aren't precision target sights anyway. They are lightweight, but the best thing about them is that if they bump into a hard surface while moving, they will just fold out of the way and spring back. While many consider the Troy sight the pinnacle of BUS (and they are very strong), they lock upright with two steel pins and will break before they fold- though, granted, this would take a seriously hard impact.

Ive never tried the Matechs, but many people who have really like them.

My only minor gripe with the Magpuls is that they have two apertures "fine" and "battle," and the "fine" hole is presented first when they are deployed . You can leave the "fine" blade flipped off with the sight folded, but it doesn't sit perfectly flush.

I have actually removed the "fine" aperture from the BUS on my CQB rifle, as I want the larger "battle" hole for quicker target aquisition.

They also make A2 sights without the carry handle-https://www.amazon.com/OZARK-ARMAMENT-Rear-Iron-Sight/dp/B013TLZ45C

AlexanderA said:

With the removable carry handle, the rear sight sits slightly higher than with the original non-removable carry handle. To match the removable carry handle sight (or any modern flip-up rear sight, really), you need a front sight tower (base) that has a small "F" marking. (It's slightly taller than the original tower.) The first thing to do is check if you have an "F" marked front sight tower. If it's a recently-made gun, chances are you have it.

Regarding flip-up rear sights, FWIW the Army uses the one made by MA Tech. I suppose that's as good as any.

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If the gun came as a flat top with an A2 style front sight base, it should indeed be marked "F" for flat top. This will match with any rear sight made for a flat top AR15.

FL-NC said:

I don't care for magpul flipups or any other type that are spring loaded in the "up" position. You can also cut down your detachable carry handle like below to lighten it up- you will still have a good adjustable sight and be able to mount a RDS on the expose forward portion of the rail to co-witness.
View attachment 1050807

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I don’t want to like it but I can’t help myself.

I have the Ma Tach USGI sight and it is relatively heavy for the category, but it is a very nice rear sight. I can see why the military chose it.

BigBlue 94 said:

If the gun came as a flat top with an A2 style front sight base, it should indeed be marked "F" for flat top. This will match with any rear sight made for a flat top AR15.

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When buying barrel assemblies with the front sight base installed, nowadays they invariably come with the "F" marked base. You can't find the older style base! This was a problem for me recently when building a classic A2 rifle. I had to use the higher front sight base and compensate by running the rear sight up way too far.

AlexanderA said:

When buying barrel assemblies with the front sight base installed, nowadays they invariably come with the "F" marked base. You can't find the older style base! This was a problem for me recently when building a classic A2 rifle. I had to use the higher front sight base and compensate by running the rear sight up way too far.

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Hah me too! Except i went with an A1 upper. Im just going to mill .040" off the sight post. That is the difference: the F-marked front sight shelf, and subsequently the sight post, is .040" higher.

AlexanderA said:

With the removable carry handle, the rear sight sits slightly higher than with the original non-removable carry handle. To match the removable carry handle sight (or any modern flip-up rear sight, really), you need a front sight tower (base) that has a small "F" marking. (It's slightly taller than the original tower.) The first thing to do is check if you have an "F" marked front sight tower. If it's a recently-made gun, chances are you have it.

Regarding flip-up rear sights, FWIW the Army uses the one made by MA Tech. I suppose that's as good as any.

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Actually, the MA-Tech version has significant issues. It was developed as an "upgrade" for the early Knights "lollipop" BUIS, with the MA Tech featuring range adjustments and a spring loaded release. When we got the "upgrade" sights, we had several of the mounting dovetails break off (resulting in the sight falling off of the weapon) and in many cases the retainer that held the sight in the down position broke, resulting in the user being unable to stow the sight in the down position. After looking at several models on the commercial market, my unit ended up purchasing the A2 BUIS made by GG&G. Some guys just kept the old Knights lollipop, and others continued using the cut down carry handles to co-witness with their M68's or EOtechs.

FL-NC said:

Actually, the MA-Tech version has significant issues. It was developed as an "upgrade" for the early Knights "lollipop" BUIS, with the MA Tech featuring range adjustments and a spring loaded release. When we got the "upgrade" sights, we had several of the mounting dovetails break off (resulting in the sight falling off of the weapon) and in many cases the retainer that held the sight in the down position broke, resulting in the user being unable to stow the sight in the down position. After looking at several models on the commercial market, my unit ended up purchasing the A2 BUIS made by GG&G. Some guys just kept the old Knights lollipop, and others continued using the cut down carry handles to co-witness with their M68's or EOtechs.

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Not sure I like their A2 style sight, but this one is interesting-
https://www.opticsplanet.com/gg-g-mad-buis-flip-up-rear-sights.html

Super low profile and multi-aperture, similar to the Spanish FR8 sight (one of my favorites).

NIGHTLORD40K said:

Not sure I like their A2 style sight, but this one is interesting

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We tried that one too. I believe the SEALs did as well. The problem we had with that one was that firing the weapon sometimes made the multiple apertures rotate. I also saw one that got stuck and frozen in place, so we rejected the MAD sight too.