AR-15 Build Tools - Lessons Learned

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  • DAVE_M

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    Apr 17, 2009
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    Every now and then there is a discussion about building AR-15's and it almost always becomes an argument. Thanks to the boom in AR sales over the last two decades, there are now more proprietary tools available than years past. These are not all necessary, but make the job much easier. Below are some of the tools I currently use and have used in the past. I'm always open to trying new things if they can be proven to be a better solution. I'll likely do this in sections, because there are a lot of things to cover.

    First tool, which is arguably the most common, is an armorer's wrench. When I first started, I did my homework and found that the Brownell's armorer's wrench was a quality Made in the USA combination wrench that works well with USGI Barrel Nuts, Castle Nuts, A2 Receiver Extensions, and A2 Flash Hiders. It can be purchased here: https://www.brownells.com/gunsmith-...renches/ar-15-armorer-s-wrench-prod80294.aspx

    What I've learned from using it is that while the double sided barrel nut wrench works well for USGI barrel nuts and some larger diameter barrel nuts where the gas tube passes through a drilled hole, it is not a universal fit for all barrel nuts. The 3/4" and 5/8" openings for use with A2 receiver extensions and flash hiders are fairly loose and can potentially mar the finish or deform parts, and while the castle nut wrench fits well, the 1/2" drive torque wrench adapter is too far away for it to be easily used to torque a castle nut. For the price, it's a hefty wrench and feels well made, but aside from being used to tear down rifles it stays in the drawer.

    Just above the Brownell's wrench is a Wheeler Engineering Delta Series Armorer's Wrench. I DO NOT RECOMMEND THIS. I originally purchased it when installing an Aero Precision BAR Barrel Nut, which only has four drilled holes for the gas tube to pass through. This required a wrench that would fit drilled holes at 3, 6, 9, and 12 o'clock. What I found was this wrench with pins at 3 and 9 o'clock. While it was useful for the few BAR barrel nuts I installed, I would not recommend using this for any other purpose. The wrench itself is made of thin flat bar, using three layers riveted together. It is fairly thick near the barrel nut, but the castle nut wrench is thin and does fits very loosely on castle nut. Again, this wrench has the 1/2" drive adapter too far away to be used for applying torque to the castle nut with a torque wrench, and neither of the open wrench slots fit well on A2 receiver extensions or flash hiders.

    Once I got into using aftermarket parts, I began to acquire proprietary wrenches. On the bottom right is a Geissele SMR Barrel Nut Wrench and to the left of it is a BCM KMR Barrel Nut Wrench. Both of these can be purchased separately and I highly recommend doing so. Among the other aftermarket barrel nut wrenches, I prefer these two specifically over any Armorer's Wrench. The Geissele barrel nut wrench is designed to remove a USGI barrel nut and install the Geissele SMR barrel nut. It can also be used, carefully, to reinstall a USGI barrel nut. The best part? It costs only $9 and doubles as a bottle opener. So while the Geissele wrench covers USGI barrel nuts, the wonderful thing about the BCM KMR barrel nut wrench is that they were clever enough to design the KMR barrel nut to be installed with a three sided castle nut wrench. This wrench can be purchased for $15 and is a great addition to the toolbox.

    Fast forward to today and I have invested a bit more into proprietary tools. First and second from the bottom left are the Forward Controls JMW (Joint Muzzle device Wrench) and JCW (Joint Castle nut Wrench). While neither are useful for barrel nuts, each of these are made to tighter tolerances and designed to be more efficient at their jobs. The JCW has two sides, both used for castle nut installation or removal. If you use QD muzzle devices for suppressors or just want to shim and time a brake, I highly suggest acquiring a JMW.

    JCW (Joint Castle nut Wrench) is a dedicated, heavy duty twin castle nut wrench, precision CNC machined from 4140 steel, heat treated and black oxided, it's something we've always wanted and needed. We couldn't find one we liked, so we answered our own prayers and made it. Like many AR users, we used either a heavy and unwieldy armoror's wrench, or a cheap stamped sheet metal castle nut wench that couldn't be used with a torque wrench, both work, but neither is great. One is overkill, the other is barely adequate. The handy JCW combines two castle nut wrenches in one. On one end, it has a conventional 3 lug castle nut wrench, spanning 180 degrees. On the other end, it has a unique two lugs wrench, spaced only 90 degrees apart. JCW measures 3.5"x 1.84" (at its widest), but is surprising heavy at 3.14oz, due to its 4140 steel construction. JCW was designed from the start to be used with a torque wrench.

    On some end plates with QD swivel sockets, the sockets housing masks a good portion of the castle nut's circumference, and there are occasions where not all 3 wrench notches are accessible.

    https://www.forwardcontrolsdesign.com/Joint-Castle-nut-Wrench_p_129.html
    https://www.forwardcontrolsdesign.com/jmw-joint-muzzle-device-wrench.html

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