Anyone have one of these? My FFL has them in stock, thinking about picking one up. And I understand there are only a few manufacturers of lowers, but do they actually finish the entire lower or just the forge? In other words, do companies like Spikes, CMMG etc do any work on the lowers like the threading or drill the holes etc? Also, does anyone know who manufactures Matrix Aerospace lowers (e.g LAR, LMT, Mega, etc)?

There are lot more than a handful of companies machining lowers.  There are only a handful making forgings, but that really isn't important to the end consumer.  If a company does their own machining or not isn't important.  QC and customer service are what's important.  Most companies sign NDAs so you'll never know for sure who machines what for who.  Also, a lot of the companies will switch vendors or get supply from multiple vendors for a multitude of reasons.  If the lower is in spec (most are) and you like the logo on it, then get it.

At what point is it regulated by the ATF? Once it is forged or machined? Who engraves the logo and the serial number?

For example, does a company like Cerro forge the lower, sends it to let's say LMT, and LMT serves as the OEM for the other companies? In this example, is Cerro or LMT regulated by the ATF. It is confusing to me since anyone can buy an 80% lower, perhaps this doesn't apply to dealers.

Also, when folks say a lower is a lower is a lower, does this take into account the machining? Not all my lowers fit the same, not sure all manufacturers use the same specs/tolerances. In theory they can all use different templates to drill the pin holes, for example.

Sorry if I am being dense, just trying to understand why "all lowers are created equal".

Once it's machined.  More accurately, once the pocket for the fire control group is machined.  You can machine everything but that and it's still a hunk of aluminum.  The company doing the machining will engrave it with their info.  Unless there's a variance in place.

In your example Cerro isn't selling lowers to LMT, just chunks of aluminum that sort of resemble a lower.  If LMT is selling completed lowers to Spikes with Spikes info on the side of the lower, then they have a variance that's already been approved by the ATF.

An instance where another company made lowers without a variance would be the older LaRue lowers that were made by SMOS.  Because there was no variance in place SMOS had their info on the lowers as the manufacturer.

So basically in the previous example, LMT would finish the lower for Spikes, and Spikes would simply resell the lower? Or is it possible Spikes would do some machining to the lower prior to selling it to Joe Q Public? Sounds like could be either.... if I understood correctly, LMT could machine the FCG pocket, engrave it and send it to Spikes, Spikes could do some additional machining before selling it to Joe Q Public.

This is why I like 80% lowers. No logo to bug the shit out of me if my tastes change later.

Generally whoever is serving as the OEM (LMT in this scenario) is going to do all of the machining.  Spikes could do additional machining to it, but it's unlikely they would.  Easier to just have LMT do any additional machining before they ship it to you.

Pic, so I don't have to search.

http://www.slickguns.com/product/forged-stripped-lower-receiver-7299

it looks like a nice lower and the company looks pretty damn legit to me.  I'd get it.

I have been a QC inspector for machine shops and fab shops most of my older adult life. When these parts are machined they don’t use templates, they are milled in CNC machines. Depending on the machine there could be as many as 6 to 8 parts milled at a time. When I look at a print for a part and it has a +/- tolerance of say .005, as long as it’s in that range it’s a good part. If company A machines the lower and positional tolerance is tight it’s still good. If company B machines an upper and their positional tolerance is wide it’s still good but you put those two parts together and your take down pins will be tight on some and loose on others. QC have to follow the specs on the print.

I have two,  only built one of em so far,  but it seems solid,  everything was in spec,  pin holes were as tight as they should be and all lined up. Mated perfectly with a standard PSA upper.   Also,  the Matrix Aerospace  lowers are supposedly the exact same ones (same manufacturer and machine,  just different logo at the end)  used in the Ruger ARs.

I keep hearing that, but are Ruger ARs highly regarded?