How to Torque an AR-15 Barrel Nut
Woody's answers are based on published federal and state law. Not legal advice. Consult a licensed attorney for your specific situation.
Torque the AR-15 barrel nut to 30-80 foot-pounds, then back it off and retorque to align the gas tube hole with the upper receiver. Use a barrel nut wrench and torque wrench for proper installation.
How This Affects Your Build
Proper barrel nut torque ensures the barrel extension locks securely into the upper receiver while maintaining correct headspace. Getting the torque right also aligns the gas tube hole with the gas key on your bolt carrier group. This is one of those steps where doing it wrong can cause serious reliability issues or even dangerous malfunctions.
The Detail
The barrel nut threading creates the primary mechanical connection between your barrel and upper receiver, so getting the torque specification right matters for both accuracy and safety. You need to apply enough force to fully seat the barrel extension into the receiver while ensuring the gas tube hole lines up properly with your gas system.
Start by hand-threading the barrel nut onto the barrel extension threads, making sure it goes on straight without cross-threading. Once it's hand-tight, use your barrel nut wrench and torque wrench to bring it up to about 30 foot-pounds initially. Check the alignment of the gas tube hole with the gas port in your upper receiver at this point.
If the hole alignment is off, you'll need to back the nut off slightly and retorque until the holes line up properly. The acceptable torque range runs from 30 to 80 foot-pounds, giving you plenty of room to find the sweet spot where everything aligns. Never exceed 80 foot-pounds, as you can damage the threads or stress the receiver.
Some builders use barrel nut shims or timing shims if they can't get proper alignment within the torque range, but most standard setups will align somewhere in that 30-80 range. Once you've got proper alignment and torque, install your gas tube through both holes to verify everything lines up correctly before moving on to the next step.
Build Impact
Getting this wrong means your gas system won't function properly, leading to short-stroking or failure to cycle. Take your time with the alignment check because rushing this step creates headaches later when you're trying to figure out why your rifle won't run reliably.