How to Pick the Best AR Handguard Length
The handguard is more than just an aesthetic choice—it’s a key interface between shooter and rifle. Handguard length affects weapon control and accessory setup. But, there is also a significant element of safety involved. Too short, you could burn your fingers; too long, you could blow them off.
When you select a handguard length, you must consider two main things: gas system length and barrel length.
Gas System Length vs. Handguard Length
How to Determine Actual Handguard Length
Nominal handguard length is generally stated as the actual handguard length. When installed, this generally translates into the distance between the forward face of the upper receiver (i.e. excluding the barrel nut threads or mounting lug), and the muzzle end of the handguard. There may be some consideration for the jam nut, if applicable to the mounting system. Check your manufacturer’s specifications for actual measurements.
The specific guidance in this article focuses on the Aero Precision Enhanced M-Lok handguards, as we use these, exclusively, on our builds.
How to Determine Minimum Handguard Length
Your nominal gas system length (i.e. pistol length, carbine length, mid length, rifle length) is associated with the length of the gas tube and the distance from the front edge of the barrel extension to the gas port on your barrel (A)
However, we need to express the gas system measurement in terms that translate to meaning for the handguard length. As such, we provide the distance from the front face of the top rail on the upper receiver (i.e. excluding barrel threads/mounting lug) to the gas port (B).
We also must factor in the length of the gas block. The gas block site over the gas port and extends both behind and in front of the gas port. The typical gas block is 1″ long, with about 3/4″ sitting forward of the center of the gas port. As such, we must add this additional value to the minimum handguard length (C).
The table below illustrates the standard measurements for the nominal gas system lengths. Note that measurement C (in bold) represents the recommended minimum handguard length for a given gas system length needed to completely cover the gas system with the handguard.
| Nominal Gas System Length | Barrel Extension to Gas Port (A) |
UR Face to Gas Port (B) |
UR Face to GB Face (C) |
|---|---|---|---|
| Pistol | 4″ | 4.5″ | 5.25″ |
| Carbine | 7″ | 7.5“ | 8.25″ |
| Mid | 9″ | 9.5″ | 10.25″ |
| Rifle | 12.5″ | 13.0″ | 13.75″ |
| Rifle + 2 | 14.5″ | 15.0″ | 15.75″ |
The table below shows general compatibility of Aero Precision Enhanced M-Lok handguards with nominal gas system lengths (note that this does not reflect the other factor, barrel length, which will be covered in the next section).
| Gas Length | 7.3" HG | 9.3" HG | 10.7" HG | 12.7" HG | 15" HG | 16.6" HG |
|---|---|---|---|---|---|---|
| Pistol | Yes | Yes | Yes | Yes | Yes | Yes |
| Carbine | No | Yes | Yes | Yes | Yes | Yes |
| Mid | No | No | Yes | Yes | Yes | Yes |
| Rifle | No | No | No | No | Yes | Yes |
| Rifle + 2 | No | No | No | No | Maybe* | Yes |
Barrel Length vs. Handguard Length
How to Determine Maximum Handguard Length
The first consideration when calculating the appropriate handguard length for a given barrel length is the type of muzzle device that will be installed, if any.
Note that the closer the end of the handguard is to the muzzle, the more likely you will get burned or otherwise injured. Push the envelope at your own risk.
If you are either not installing a muzzle device or are installing a standard “side blast” flash hider, compensator, or muzzle brake, your handguard MUST NOT extend beyond the crown of the barrel. Said another way, the crown of your barrel should extend beyond the handguard. It is typically ok for the threads to lie within the handguard for most muzzle devices.
Recessed Muzzle Devices
DO NOT use a muzzle brake, compensator, or flash hider that directs the hot gas radially (up, down, to the sides) with a handguard that extends beyond the crown of the barrel. The example below shows what NOT to do:
If you use a handguard that is too long for your barrel and muzzle device, you will, at the very least, get some nasty stuff happening to your handguard where the gas is expelled. At worst, you will burn the sh*t out of your hand or lose fingers. The image below illustrates the risk of what can happen:
With that said, the barrel may be shorter than the handguard IF either:
- You are using a blast forwarding device (e.g. Noveske KX3, Troy Claymore). In this case, the handguard must not extend beyond the forward face of the device.
- You will be using the firearm with a dedicated suppressor (i.e. you will never fire the gun without the suppressor installed). In this case, the handguard must not extend beyond the forward face of the suppressor.
The minimum handguard length, in this case, can be calculated by considering the composite length of the barrel and muzzle device/suppressor, with consideration of the overlap between the two.
Example Calculation of Maximum Handguard Length for Recessed Muzzle Devices
For demonstration, we will assume that we have selected a 10.5″ barrel and a 2.5″ blast-forwarding device (BFD). The goal is to not have the handguard extend beyond the end of the muzzle device.
The first component of the calculation is the combined length of the barrel and muzzle device.
When using a BFD or suppressor, you can use the combined length of the device and barrel barrel (barrel length plus muzzle device length) when calculating the safe handguard length. Using our example, the combined length of the barrel and BFD would be 13″ (10″ plus 2.5″).
However, this isn’t entirely complete or accurate.
Next, we have to adjust the combined length to account for the overlap between the two. To calculate the overlap, we must account for the length of the threaded portion of the barrel, less any crush washer or shim depth. The standard threads on an AR-15 barrel are between 0.600″ and 0.625″ and a crush washer (uncompressed; if applicable) is 0.15″ in depth. So, the overlap is calculated as thread length minus crush washer/shim thickness. In our example, the overlap would be 0.475″ (0.625″ minus 0.15″)
The table below lists the minimum barrel lengths for the different lengths of Aero Precision Enhanced M-Lok handguards.
| Nominal Handguard Length | Standard Minimum Barrel Length1 | BFD/Suppressor Minimum Barrel Length2 |
|---|---|---|
| 7.3″ | 7.3″ | 5.275″ |
| 9.3″ | 9.3″ | 7.275″ |
| 10.7″ | 10.7″ | 8.675″ |
| 12.7″ | 12.7″ | 10.675″ |
| 15″ | 15″ | 12.975″ |
| 16.6″ | 16.6″ | 14.575″ |
- Handguard shall not extend beyond the crown of the barrel.
- Assuming a 2.5″ blast forwarding device or dedicated suppressor (for context, the Noveske KX3 “Flaming Pig” is 3.25″ long). Use the Calculation to calculate the appropriate length for your barrel and muzzle device/suppressor.
Free-Float Handguard Length Selection
The table below illustrates the minimum (based on gas system length) and maximum (based on barrel length) free-float handguard lengths for a given barrel/gas system. We provide our recommendation for each, which is a reflection of a reasonable safety margin from the muzzle and the assumption that you are using a standard, radially-discharging muzzle device (flash hider, compensator, muzzle brake, etc.).
Frequently Asked Questions
How do I choose the best AR-15 handguard for my build?
Match the handguard to your barrel length and gas system.
If using a 2-piece drop-in handguard, the handguard needs to match the gas system length.
If using a free-float handguard, ensure it covers the gas block, does not extend beyond the muzzle or over the exhaust path, and aligns with your intended use—longer for full-length rails and accessories, shorter for compact builds.
What’s better: free float or drop-in handguards?
Free float handguards improve accuracy and provide more mounting space. Drop-in handguards are simpler, budget-friendly, and work well for standard military-style builds with delta rings.
Are handguards compatible with different gas systems?
It depends.
2-piece drop-in handguards must be matched to the gas system length.
Free float handguards should cover the gas block. If it is too short, it will expose the hot metal of the gas system.
What’s the difference between carbine and midlength handguards?
Carbine-length handguards are about 6.5”, designed for carbine gas systems. Midlength handguards are roughly 9” and used with midlength gas systems. Midlength setups provide a smoother recoil impulse and more handguard space.
Can I use a rifle length handguard on a carbine gas system?
Yes, but you need a low-profile gas block and a free-float handguard that clears it. A rifle-length handguard on a carbine gas system is a common aesthetic choice in modern builds.
Is there a chart showing AR-15 barrel and handguard length compatibility?
Yes—our guide includes a detailed AR-15 handguard length chart, helping you match handguard length to barrel and gas system type.
What are the advantages of a midlength vs carbine handguard?
Midlength gas systems offer smoother recoil and midlength handguards offer more grip space and improved sight radius. Carbine handguards are more compact and compatible with older or military-style carbines.
What is the best AR-15 handguard length for a 10.5 inch barrel?
If using a 2-piece drop-in handguard, match the length to the gas system.
If using a free-float handguard:
- Pistol Length: We recommend 9-10″ for a 10.5″ barrel with a pistol length gas system, but 5.25-10.5″ will work. A longer handguard may be used if paired with a blast forwarding device or dedicated suppressor.
- Carbine Length: We recommend 9-10″ for a 10.5″ barrel with a carbine length gas system, but 8.25-10.5″ will work. A longer handguard may be used if paired with a blast forwarding device or dedicated suppressor.
A longer handguard will offer maximum coverage and rail real estate.
Depending on the design of the muzzle device, a safety margin may be desired (we recommend limiting the handguard length to half an inch shorter than the barrel length for radially-discharging muzzle devices).
What is the best AR-15 handguard length for a 14.5 inch barrel?
If using a 2-piece drop-in handguard, match the length to the gas system.
If using a free-float handguard:
- Pistol Length: We recommend 12.5-14″ for a 14.5″ barrel with a pistol length gas system, but 5.25-14.5″ will work. A longer handguard may be used if paired with a blast forwarding device or dedicated suppressor.
- Carbine Length: We recommend 12.5-14″ for a 14.5″ barrel with a carbine length gas system, but 8.25-14.5″ will work. A longer handguard may be used if paired with a blast forwarding device or dedicated suppressor.
- Mid Length: We recommend 12.5-14″ for a 14.5″ barrel with a mid length gas system, but 10.25-14.5″ will work. A longer handguard may be used if paired with a blast forwarding device or dedicated suppressor.
A longer handguard will offer maximum coverage and rail real estate.
Depending on the design of the muzzle device, a safety margin may be desired (we recommend limiting the handguard length to half an inch shorter than the barrel length for radially-discharging muzzle devices).
What is the best AR-15 handguard length for a 16 inch barrel?
If using a 2-piece drop-in handguard, match the length to the gas system.
If using a free-float handguard:
- Pistol Length: We recommend 12.5-15″ for a 16″ barrel with a pistol length gas system, but 5.25-16″ will work. A longer handguard may be used if paired with a blast forwarding device or dedicated suppressor.
- Carbine Length: We recommend 12.5-15″ for a 16″ barrel with a carbine length gas system, but 8.25-16″ will work. A longer handguard may be used if paired with a blast forwarding device or dedicated suppressor.
- Mid Length: We recommend 12.5-15″ for a 16″ barrel with a mid length gas system, but 10.25-16″ will work. A longer handguard may be used if paired with a blast forwarding device or dedicated suppressor.
- Rifle Length: We recommend 15″ for a 16″ barrel with a rifle length gas system, but 13.75-16″ will work. A longer handguard may be used if paired with a blast forwarding device or dedicated suppressor.
A longer handguard will offer maximum coverage and rail real estate.
Depending on the design of the muzzle device, a safety margin may be desired (we recommend limiting the handguard length to half an inch shorter than the barrel length for radially-discharging muzzle devices).
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