Flat-Top AR-15 Rifles Using Removable Carry Handle:
There are removable carry handles that fit on flat-top rifles. It is possible to mount optics on top of the carry handle, but this is inefficient and mounts the reticle or crosshairs of the optic higher than the optimal 2.5 inches above the bore (the height of the front sight and the rear carry handle sight). If you want to mount optics on the rifle, remove the carry handle and mount them directly to the rifle. Don’t mount any optics to the top of it. This defeats the purpose of the removable carry handle. Remove it and mount the optics to the rifle’s rail. If you want to use the A2 style sights of the removable carry hand then keep reading.
Removable Carry Handle Use With Fixed Factory Front Sight Base (FSB):
Most AR15 style rifles built in the past ten to fifteen years do not have a built-in carry handle / rear sight assembly, but rather a “Picatinny rail” that allows the user to have a choice as to mount holographic sights, red-dot sights, magnified optics, simple rear sights, or even a removable carry handle / rear sight assembly. These are referred to as “flat top” rifles (pictured right). In the past, anyone wanting to mount optics on top of their AR-15 style rifles were forced to use some type of adaptor to mount their optics on top of the fixed carry handle. This set the optics too high to take advantage of the 5.56x45mm NATO rounds fairly flat trajectory, and it set the optic too high for the shooter to get a good cheek weld on the stock. The flat-top design allows you to mount your optics so that the aiming reticle is the same height above bore as the tradition fixed “iron sights”.
Potential Problems Mounting A Removable Carry Handle:
If your new flat-top rifle ships with a removable carry handle, then the follow information will not be relevant.
If you own a flat-top rifle and decide to purchase a removable carry handle sight, then there are some pitfalls that you need to be aware of.
If you buy a flat-top with a fixed sight base and you decide that you want to purchase a removable carry handle to use as the rear sight then there are some factors to consider. There is a specific sight height that is considered “Mil-Spec”. Not all rifles are “Mil-Spec”, and you will find rifle manufactures that use sight towers that are slightly shorter (sometimes referred to a “commercial height”, the distance almost unnoticeable to the untrained eye). If you try to use a detachable carry handle with a Mil-Spec height rear sight on a rifle with a front sight that is “commercial height” then you find it impossible to zero your rifle.
Is Your Front Sight Base Mil-Spec Or Not?:
Mil-Spec front sight bases for A-3 (removable carry handle / flat-top) AR-15 rifles are taller than older A-1 and A-2 (fixed carry handle) rifles. The way to tell whether or not you have a mil-spec FSB is that it is marked with an engraved or raised “F” on the left side of the front sight base’s forging (as seen in the photo to the right). There may be other markings to differentiate the company of origin, but a “F” on the left side of the front sight post is the only way to be sure. If you have an “F” then you can simply add a mil-spec removable carry handle and skip this section.
Issues With Removable Carry Handles On Rifles With Non Mil-Spec FSB:
There are a few manufacturers whose “commercial grade” rifles are equipped with FSBs that are not quite exactly Mil-Spec height. Bushmaster still uses the older, traditional shorter A-2 front sight base on their A-3 (removable carry handle) rifles, as do DPMS and several other manufacturers.
Technically the all front sight bases are the same height, but the top part of the FSB where the post extends from sits higher than a standard “commercial” FSB, as seen in the photo to the right.
To make up for shorter FSB, Bushmaster, DPMS, and some other manufacturers use shorter removable carry handles. The difference between a Mil-Spec and commercial removable carry handle is very difficult to tell apart unless you have one of each to compare, or have a dial or digital caliper to measure. Remember, a non Mil-Spec carry handle will not work with a “F” marked Mil-Spec height FSB, and as stated earlier, a Mil-Spec carry handle will not work with a non “F” marked “commercial height” FSB.
You will not be able to properly zero your sights if they are mismatched. Remember that your elevation changes will be made with the front sight. You will not be able to zero the rifle because you won’t be able to raise the front sight post enough without the front sight post backing out of the FSB (as seen in the photo to the right). Completely unacceptable.
Pictured right is a comparison of the Mil-Spec front sight post (left) that sits on a taller front sight base compared to the .040″ taller post (right) that is required on the shorter “commercial height” sight base to make it work with a mil-spec removable carry handle. If you are going to mount a backup rear sight on a rifle with a fixed, “commercial height” FSB, then you will need to replace the original front sight post (pictured left in the photo to the right) with a slightly taller (.04″) front sight post (pictured on the right in the photo to the right) that can be ordered from Windham Weaponry and shipped for around $10.
Replacing the original front sight post will require a front sight tool AR-15 front sight tool that can be ordered from the same company. Simply use the tool to simultaneously hold in the front post retaining pin while unscrewing the sight post out of the sight base. It’s very easy with the tool, and frustrating and time-consuming without it.
It is interesting to note that replacing the front sight post is more critical on Bushmaster carbines, but may not be necessary on full-length rifles with 20″ barrels.
Before you start ordering parts for replacing your removable carry handle or front sight post for your “commercial grade” rifle, verify that it is not marked with the raised “F”. Older Bushmasters were not. There is a chance that since Bushmaster is under new ownership that newer rifles may have the correct height Mil-Spec front sight tower and sight post that will work with Mil-Spec backup iron sights.
How To Zero Your The Sights On Your Removable Carry Handle:
Once you have properly installed your removable carry handle then you will need to zero the sights. Be sure to check out:
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- Savannah Arsenal’s AR-15 / M4 / M-16 Page
- Savannah Arsenal’s Tactical Rifle Optics
- Savannah Arsenal’s AR-15 — Sights and Optics Considerations
- AR-15 — Rear Sight & Optics With Front Sight Base
- Savannah Arsenal’s AR-15 — Mounting Backup “Iron” Sights (BUIS)
- Savannah Arsenal’s AR-15 — Mounting Removable Carry Handles
- Savannah Arsenal’s AR-15 — Methods For Zeroing A2 Type Sights