Aero Precision BAR barrel nut install

Can someone help me decipher this "gauge" for shimming the Aero Precision BAR barrel nut? I will need to use shims to get the gas tube holes aligned. For the life of me, I can't figure out the logic behind this chart. I'm assuming the red circle is the "target".

 

What size shims are you using?

 

.002 (8x) is what comes in the box

 

Are there markings on that gauge they are showing in the picture? You can see how from 13 to 9 there are four steps thus four shims. Luckily they included the .02 size.

Should post this on the AR15 BS thread. Those guys probably will have more info.

 

No. No other instructions other than what's on that single page. Doesn't indicate what to torque it to before measuring. Doesn't indicate what the red ring indicates (it's obviously of some significance).

I got it figured out through trial and error. Had to use 4 shims and 45 ft lbs.

 

That's how I would have done it myself. Still strange there is no indication marks on the gauge.

 

Looks to me like you just add the appropriate number of shims to allow one of the four holes to line up with the gas port at 12 o'clock.

With the above diagram it seems like with zero shim (.000) none of the holes align with the gas port. The graduations are showing that with .008 worth of shim, the hole that is presently at the .000 location with be rotated to about the 12 o'clock position.

The red circle looks like it indicates a cut away, so you can see the gas port behind the barrel nut, and is just there to make the drawing a bit more clear.

Ultimately you might just have to assemble and disassemble a few times with varying shims until you get the alignment you need. It's like each .002 shim allows for a 4 degree reduction in rotation, or something like that.

The drawing is kinda convoluted.

 

I know this was solved but this is one of the top Google hits for searches related to Aero Precision BAR nuts so I figured I'd explain it more and link the manual.

https://www.aeroprecisionusa.com/media/downloadable/bar-barrel-nut-instructions.pdf is the full manual. The page before the image here explains it better. In short, the red dot needs to go to the 12:00 position, but any of the four would do. You just shim whichever makes the most sense - either shims and an "earlier" hole, or no shims and slightly more torque, up to 45 pounds and a "later" hole, if one is really close.