Correct barrel installation is very important. An incorrectly installed barrel can cause serious injury or death. We are going to discuss the correct way to get your barrel installed. First thing we need to do is gather up some tools and supplies:
Armorers wrench, torque wrench, punch, gas tube alignment rod, receiver clamp and / or padded vise, and grease. A grease like AeroShell 33MS or MCARBO designed for aircraft and graphite free is what you will need. Without the proper grease, your upper and barrel could eventually suffer from galvanic corrosion, galling, crack and come loose.
1. Grease the barrel extension prior to installing into the receiver.
2. Align the index pin with the recess in the upper receiver.
3. Push the barrel and upper together so the index pin fits in the slot. It is OK to use a rubber mallet to install the barrel to the upper if things are too tight.
4. Apply grease to the threads of the upper receiver and hand tighten the barrel nut assembly on to the upper.
5. With your torque wrench and armorers tool tighten and loosen the nut 3 times to seat the threads. Use the torque wrench to tighten only! Use your armors wrench to loosen. The goal is to align the space between the teeth at 12 o’clock.
6. Torque from a minimum of 30 ft lbs to a maximum of 80 ft lbs. Your goal is to align a gap between the teeth to 12 o clock of the upper to permit the gas tube to slide through. Once torqued, the gap in the delta ring, weld spring, and C clamp will need to be positioned to 12 o’clock as well.
a.) If it won’t line up, the easiest, and safest method is to order a barrel nut shim. If you are going to be doing several of these, might be worth having a few on hand. These are thin shims that will be installed in the barrel nut to help align the next gap / tooth. Follow the instructions included with the kit and it should fix any alignment issues.
7. Slide the gas tube into the upper receiver.
8. Push the front of the gas tube into the front sight / gas block base. There will be two holes on the end that goes to the sight post / gas block, one hole for the gas, another for the roll pin. Align the holes and use a punch to install the roll pin.
9. Drop on your hand guards and you are done.