Dear internet people, I am curious about something. I've noticed that my Aero lowers consistently have less bolt catch engagement compared to my other lowers. The first lower pictured below closed the bolt on itself when I slapped a mag in during a mag change; I ended up moving some of it's parts to a different lower and it's been sitting in my parts pile since. I bumped into it again the other day looking for something else and it got me thinking about this again.

So...does anyone else with a bunch of different lowers notice this as well?

I think it'd be a fair guess to assume their catch slot isn't deep enough, the spring hole is too deep, and/or the spring from the lpk is. Without having hands on or accurate measurements, that's all I got.

It's important to note that tension from the mag spring/follower is what engages the bolt catch on an empty mag.

Assuming the magazine in question works in other rifles ok, it may be that the bolt catch spring is too stout or the pocket for the bolt catch spring is too shallow.  In either case, the magazine spring/follower is not strong enough to over power the extra tension and push the bolt catch up all the way on an empty mag.

I had a similar issue with an old Cav15 lower where the pocket for the bolt catch spring was too shallow (common issue).  The shallow pocket resulted in too much tension in the bolt catch spring. It therefore had to be trimmed so the mag spring/follower tension was enough to push the bolt catch all the way up and hold the bolt open.

Edit: Trimming the bolt catch spring is a good place to start as it's the least expensive part.  If you decide to do it, trim half a coil at a time and test fit.  You can use a takedown pin detent or punch as a slave pin for test fitting to make things easier.  It's important to go incrementally as too little tension on the catch may cause it to pop up when you dont want it too.

These are all locked open manually with the bolt catch depressed as far as it will go. My anecdotal observation is that the pocket on the Aero lowers are a tad shallower than others, preventing the bolt catch from rotating up as high as the other lowers pictured.

What I’d like to know is if other people observe the same with their lowers.

In that case, I suspect you're correct the pocket for the catch is shallow.  I've never seen it before for what it's worth.  You could try and fit the back of the bolt catch to allow more rotation.

Are all the bolt stops on all those guns the same height when not engaged?  Could be the stop itself is lower than typical spec.

While a different brand, I feel something related may be wrong with my ADM4 lower. I get about as much engagement as OP does with his g$ lower when using the regular bolt catch on the left side, when I use the lever on the right side it looks more like the aero lowers. I've also had an issue that I've never had with any AR ever before- when I am handling the rifle with the bolt locked to the rear, sometimes without me pressing on either bolt release the bolt will drop. For a while I thought I was just being sloppy with my trigger finger placement, but then I had it happen when I was putting the rifle back in my safe while holding it by the handguard. It happens primarily when I have used the right side lever to lock the bolt back, however it has also happened (I believe) when the LRBHO was engaged.