Have you ever heard of bending an Upper receiver?

[Keep The Change]

Well, since everyone seems to be chiming in.LOL

Heres my opinion:

A barrel nut screws on to the receiver. Period. If you lube the receiver threads and the front of the barrel extension, almost every single drop of torque is directly between the barrel nut and the receiver threads. Using a clamshell or cutting boards keeps it there. I use a clamshell with an anti-crush insert.

When you use a "reaction rod" you are no longer supporting the receiver at all. You are fixing the barrel extension in place. The barrel extension isn't receiving the barrel nut, the receiver is... When you torque the barrel nut onto the receiver threads, the receiver tries to turn (communicating the torque on down the line). The only thing resisting that torque is the barrel extension's index pin. Otherwise your receiver would simply spin in circles.

Using the other Brownell's rod (while fixing the barrel nut wrench in a vise) does the exact same thing in the opposite direction. The rod turns the barrel extension. The barrel extension would then simply spin forever unless that rotational torque is then transmitted to the receiver by the index pin. The index pin spins the receiver, and the receiver (where the threads are--- not on the barrel extension) gets torqued into the barrel nut.

Whichever rod you use, it transmits torque through the receiver via the barrel extension index pin. There's absolutely no way around that.

You are correct, I stand corrected.
The index pin will still be loading up the receiver when using the reaction rod. I was ignoring the torque that will still go into the receiver due to friction at the threads.


The torqueing of the nut creates friction at the threads and at the flange of extension/barrel nut. Also the turning of the nut puts tension in the receiver at the threads, creating more and more friction as torque load increases.

Using clamshell type or cutting board config:
-The receiver wants to rotate due to friction in threads. It is prevented by the vice/clamping device and the torque is absorbed in receiver cylinder. The index pin will contact the upper due to friction load created at the extension flange & nut interfaces. That friction will cause the extension to rotate and put the pin in contact with the upper.

*The receiver cylinder where it is clamped by the vice reacts the torque generated by the thread friction.
*The index pin contacting the receiver is reacting the torque created by friction btwn extension flange and barrel nut.
*Torques created by 2 notes above, create torsion in the upper at the location it is clamped.


Using just the reaction rod:
-The upper is rotated when the torqueing begins due to same friction at threads. It is rotated till it bumps into index pin.

*The index pin is now reacting the torque created by the thread friction.
*The reaction rod is now reacting the torque created by the extension flange & barrel nut friction. This is the only thing it can react.
*Now the upper is only reacting the torque created by the thread friction at the index pin.

So the reaction rod helps reduce the torsion the upper has to take, but it still takes torsion at the index pin contact.

Thanks for correcting me Variable. I didn't think it through completely.