Barrel Extension Separation!

[LRRPF52]

Whenever doing any type of muzzle device work, you only clamp the barrel in a vice.

The Reaction Rod or similar devices are meant for barrel nut installation, nut muzzle device work.

It makes zero sense to isolate some other part of the rifle other than the barrel, especially the barrel extension, when doing muzzle device work.

Also, per the M4 TDP, you are not supposed to drill and pin the barrel extension index pin into the threads of the barrel tennon. It is a press-fit operation for indexing the barrel and gas port only, not intended to secure the fit of the barrel extension to the barrel, since the torque spec for installing extensions is quite high, well beyond what most people are capable of achieving without a cheater bar and a heavy vice.

In every instance I've seen mention of someone un-torquing their barrel from the extension, it has been doing some kind of muzzle device work without isolating the barrel, with a few exceptions being Radical Firearms 7.62x39 barrels un-torquing just from firing.

I've also addressed the melonite/QPQ process before here where the coefficient of thermal expansion difference between the steel alloy used for the extension and that used for the barrel can create a problem during nitriding if the nitride shop and client are not on the same sheet of music as to materials and processes.

Since nitriding has become so common in the AR15 barrel industry, these issues have been dialed-in by companies that have been around for a while, whereas new entrants to the market looking at new production lines will have to learn this the hard way. Precision Firearms has been providing quality nitrided barrels to the market for the better part of a decade, so if there was a problem on that end, it was a fluke and they'll handle it.

Another thing that gets overlooked is the issue of muzzle devices that impart torque onto the barrel under fire. We had this problem with a certain flash hider when I did testing for a well-known rifle manufacturer over a decade ago. The Smith Enterprises Vortex FH had a RH twist to it, so it could be installed not even hand-tight, but would require an end mill vice and cheater bar to remove after a low round count. The reason it was a problem for us was because of accuracy. Each firing would induce significant torque stress onto the muzzle threads, and affect group sizes on target. It's an awesome FH for low light when reducing flash to a minimum, but there were major accuracy trade-offs we experienced.



These were heavy bolt rifles with Krieger barrels that were capable of 1/4-1/2 MOA without the Vortex FH. I think we were seeing groups open up to 1.5" or more.

Every variable needs to be accounted for when you change something. Looking at the EFAB, I'm not seeing the kinds of shaping that would contribute to torque, but I'm also not ruling it out.

Either way, using the Reaction Rod to remove the device would contribute to un-torquing the barrel from the extension, provided you exceeded the torque value at the barrel tennon/extension mate-up.