(Barrel Blank)

What is the proper procedure to install the guide pin in an AR extension..ie does the pin hole need to be cut into the threads to prevent barrel twist?

According to Brownells Gunsmithing guide....

Now, the extension can be torqued on. Poyer’s book says the torque specification for the extension is 160 ft-lbs. To me, this seems excessive. Mark Hunt tells me he uses 25 ft-lbs. on his extensions. I am inclined to use the old German torque spec “gooduntight”and some Loctite #290 green thread locker (#532-290-006). After confirming that the headspace is correct, I can then install the locator pin (#231-000-082), which is simply pressed or driven into the hole in the extension.

Weird, I have that page saved in my favorites, I click on it and it takes me right to Brownells tech page on AR barrels. I copy and past the address as normal and the link is an error every time.

https://www.brownells.com/aspx/learn/learndetail.aspx?lid=16219

PR361 Thanks for the info (the link wasn't working but not needed anyway).

BTW: This is how the barrel blank arrived..extension installed and pin on the side.

Just tap it in until flush with the extension collar, be careful to not ding the extension, then install as normal.

The only function of the pin is to prevent the barrel assembly from rotating in the upper receiver, it does not secure the extension to the barrel itself.

For anyone thinking about such functionality, there is not enough thickness in the chamber wall to be able to drill into the barrel itself for a longer pin.

Fools who only torque barrel extensions to 25 ft/lbs are why people have barrels come loose from barrel extensions. If the correct torque is used, it will not come off.

Be prepared in case you need to shorten the pin a little. My .300 blackout barrel made my AAC shipped with the pin separate. After driving it till it was bottomed out, it was up too high. When threading on the barrel nut the threads were hitting the pin. I had to remove a couple thousandths. I could have forced the nut over it, but I didn’t want to do that. I only had to remove about the thickness of a piece of paper to be able to spin the nut on with just my fingers.