Discovered an extra hole in my lower.

And my good buddy @11B CIB learned me exactly what was. Nice!





It's for taking up the slop between the lower and upper. I hadn't seent this before, but I still consider myself a n00b when it comes to everything AR.

This is an aero lower, so I decided to check my other aero lower. No hole, but I have a really good relationship with the machine shop down the road from where I work.

Barnes (BPM) has those but they work different. Not through holes.


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Too bad it’s not this one:




You could impulse buy a Full Auto lower one day

My wife’s Mega Arms billet lower has the tension screw as well, oddly enough it doesn’t need it because the fit between the upper and lower is better than any AR I’ve ever owned, even my BCM which has just a tiny bit of wiggle, but it’s there.

My PSAs on the other hand could really benefit from them since they have a good bit of play, granted they are not precision guns or anything but it still bothers me enough that I put “accuwedges” in them.

My Mega and Hogan have it with a poly tipped set screw.

Most of my lowers are Aero because I like that screw being there to get rid of the play between upper and lower. I tried the little plastic pieces that Ergo makes that is supposed to get rid of the play too. The plastic pieces were a pain trying to get the two halves to fit together.

whew.... I was worried this was going to be a biology lecture...

Dang I was hoping for one of those pawnshop finds that turns out to be an illegal blessing.

InertOrd13 said:

Most of my lowers are Aero because I like that screw being there to get rid of the play between upper and lower. I tried the little plastic pieces that Ergo makes that is supposed to get rid of the play too. The plastic pieces were a pain trying to get the two halves to fit together.

Click to expand...

I’ve used those in a couple and had to trim some of the bottom off each time...make it a snug fit though.