Geissele Reaction Rod

    Geissele Reaction Rod!

    As many readers know my family and I have a cattle ranch in the highlands of central New Mexico. In order to effectively manage our herds and mitigate calf mortality, coyotes and other predators must be culled. Aside from coyotes…there has been a recent surge in cattle theft across the Western States. The idea of coming across cattle thieves armed with a scoped 30-06 hunting rifle personally does not sit well with me. Usually when I go to the ranch I have at least a handgun, but with the rise in cattle theft a Smith and Wesson M&P15, accompanied by a handful of standard capacity (30 round) magazines, has been my primary ranch companion.

    My Primary ranch rifle.

    My Primary ranch rifle.

    My M&P-15 started life out as an M&P-15 Sport.  What attracted me to the Sport was the fact that the rifle featured a 4140 1/8 twist 5R (5 Groove rifling) barrel. Having a 1/8 twist barrel offers me the versatility to shoot 52 to 77 grain bullets. The gun easily groups about ½ MOA with Hornady Match 75 grain BTHP’s and will hold about 1 MOA with Federal 55 grain XM193. Borrowing from its sister brand, Thompson/Center, Smith and Wesson incorporated 5R, or 5 groove rifling. 5 groove rifling incorporates 5 grooves and 5 lands as opposed to the traditional 6. The theory is that the bullet experiences less deformation while going down the barrel and will experience an increase in velocity due to a less steep angle between the land and groove. This gentle angle theoretically lets less gas around the bullet while the bullet is still in the bore.

    Is there less deformation and more velocity with a 5R barrel? An upcoming article will explore this question in greater detail.

    M&P 15 without forward assist or dust cover.

    M&P 15 without forward assist or dust cover.

    The rifle has been highly modified. I added a Troy MRF-R 12” to utilize a more contemporary firing grip on the rifle as well as have a place to mount a flashlight and a bipod. I added a Magpul MOE pistol grip, as well as a B5 SOPMOD stock. I store small vital components in the stock and grip: CR123 batteries, gas rings, extractor/extractor spring/O ring, spare firing pin, and the front sight adjustment tool that came with my Magpul MBUS front sight. I also run a Magpul B.A.D lever. Smith and Wesson used 7075 T6 Type 3 Hard Coat Anodized aluminum for the lower and upper receivers. They chromed the gas key and the bolt carrier. The gun comes with the standard carbine length gas system. I am extremely pleased with the rifle and after several thousand rounds of Federal XM193 the rifle has never had a malfunction. My only complaint about the rifle is that it does not come with a forward assist or an ejection port cover assembly/dust cover.

    Enter the Geissele Reaction Rod.

    A quick call to Bravo Company Manufacturing and I had a stripped upper receiver, a forward assist assembly, and an ejection port cover assembly. Though I have swapped many barrels and rebuilt many upper receiver assemblies, it is a task I loathe. Traditionally I have used the clamp method, in which the upper receiver is pinched between a Model 1 upper receiver block, then tightened in a vise. This method can put a lot of stress on the upper receiver, mar the hard coat finish, or even break the receiver index pin on the barrel (Something I have seen happen….which can be fixed by a competent welder). I was not looking forward to swapping the upper receivers until I came across the Geissele Reaction Rod while surfing around the MilitaryTimes/GearScout blog. Intrigued, I ordered the Reaction Rod from the Geissele Automatics Website.

     The Geissele reaction rod requires a heady duty vise to work properly.

    The Geissele reaction rod requires a heady duty vise to work properly.

    The Geissele reaction rod is made of 4140 Chrome moly steel. The rod securely holds an upper receiver by interfacing with the barrel extension on a standard Ar15/M16 barrel. The rod is precision fit to the upper receiver and there is ABSOLUTELY NO WOBBLE between the rod and the upper receiver. Aside from being used to tighten the barrel nut on an Ar-15/M16, the rod can be used to install/remove flash hiders and muzzle brakes, attach scopes and accessories, and for general maintenance.

    Torquing on a Vortex Viper PST 2.5-10.

    Torquing on a Vortex Viper PST 2.5-10.

    The Geissele Reaction Rod is an amazing product! Removing the barrel from my M&P-15 was extremely easy. After tightening the rod to the vise, I slid the receiver onto the rod and aligned the receiver index pin to the receiver. I  hand-tightened the barrel nut and was pleasantly surprised how little energy it took when my torque wrench clicked to indicate that the barrel nut had reached the required 80ft/lb. of torque. Rotating the upper receiver on the rod 180 degrees, I installed the forward assist. Another 90 degree turn and I installed the ejection port cover assembly. Adjusting the rod perpendicular to my workstation, I reinstalled the gas tube, Troy hand guard, and the Vortex PST riflescope.


    Final thoughts.

    The Geissele reaction rod is a product that armorers in the industry have sorely needed. The engineering, manufacture and finish of the product are excellent, and exactly what you would expect from Bill Geissele. Armorers should note that this product will require a very strong and securely attached vise. If you are not an armorer and have no desire to swap barrels and build upper receivers, you can still utilize this tool for installing forearms, gas blocks, back-up sights, accessories, and muzzle devices. I can’t wait to use this product again.

    Do you have any experience with the Geissele reaction rod? Tips, questions and gripes are welcome in the comments below.

    Load that bipod! Stay safe!

    John Noveske 1976 - 2013. Rest in Peace amigo.

    John Noveske 1976 – 2013. Rest in Peace amigo.



    Thomas Gomez

    Thomas Gomez currently resides in the mountains of central New Mexico. He has an M.B.A, an Ar-15/M16/M4 armorer certification from Specialized Armament Warehouse as well as a Glock armorer certification. Aside from writing for The Firearm Blog he works as a Clinical Analyst for a large Hospital. He spends his free time farming, ranching, hiking, fly-fishing and hunting in the beautiful forests and prairies of New Mexico. He can be reached at [email protected]