View Full Version : Aero Lower Out of Spec? - I think so

30 April 2017, 19:55
Started a new build this evening. When I got to the pivot pin install, the build came to a quick halt. After installing the pivot pin, I found that the pin would NOT move by thumb pressure either way. I was stumped. Uninstalling wasn't too difficult with the hole through the pivot pin. No big deal there. I double checked the spring I used - correct. The detent was also correct. I had also used the correct pin. Couldn't figure it out. Then, I had an idea. I did a web search for the correct depth of the recess for the spring and detent. On a site I found that the "correct" depth of the recess was 1.125". I measured the recess on my Aero lower and found that it was 1". Aha! Too much spring tension due to a too short recess. My first move was to find my cordless drill. I planned to drill another 0.125" to achieve the "correct" depth. Thank goodness the batteries were dead. While I was waiting and mildly fuming, common sense smacked me in the head. I decided to snip 1/8" from the pivot pin spring. I did and the pivot pin installed with no problems. What felt like the correct thumb pressure to move the pivot pin in and out was achieved.

My question is this: Is the 1.125" depth correct?/Is my Aero lower out of spec?

30 April 2017, 21:24
If it is def 1" then yes, it's slightly out of spec, by .125 +/- .010"

I've never encountered this exact issue on an Aero lower, my guess would be a stuck chip, piece of media from the ano prep process, burr, etc. If your pivot pin detent ever starts to seem too "loose" and I'm right, the culprit went away somehow (worked itself loose, fell out the access hole, etc) and if it does, just put a regular spring back in. Nothing to fret over.

By chance... is this a cerakoted "special" lower?

30 April 2017, 22:11
By chance... is this a cerakoted "special" lower?

No, just a regular anodized lower. I didn't mention that I hand spun a drill bit in the recess to check for any loose material. It bottomed out nice and clean and didn't loosen anything up. If something is in there and comes loose later, then it certainly would be an easy fix as you said.

The whole episode is odd as I've never had trouble with any Aero receiver ever.