The Anderson Manufacturing AR-15 Complete Lower Receiver is a CNC machined 7075 T6 forged aluminum lower that ships ready to pair with any mil-spec upper. It is marked "Multi-Cal" and accepts both 5.56 NATO and .223 Remington. The finish is Black Type III hard coat anodized. 
 

Key Specifications 

• Condition: New in Box 
• Finish: Black 
• Manufacturer: Anderson Manufacturing 
• Manufacturer Part Number: B2K402A000 
• Model: AR-15 Complete Lower Receiver 
• Type: Lowers 
• UPC: 784672106757 
   

Features 

The receiver is machined from 7075 T6 forged aluminum — the same alloy spec used by mil-spec uppers. The hard coat anodize is durable and holds up to normal handling without chipping. 
 
An integral open trigger guard and standard M4 grip profile are built in. Anderson includes a lower parts kit already installed, along with a mil-spec 6-position buffer tube kit, so the lower is complete and ready for an upper out of the box. 
 
The "Multi-Cal" marking covers both 5.56 NATO and .223 Remington, which covers the two most common AR-15 chamberings without needing a caliber-specific lower.

The Anderson lower gets recommended frequently as a budget-friendly starting point for first AR-15 builds. Most owners find the machining clean enough that parts drop in without fitting issues, and compatibility with standard mil-spec components is generally solid.

The main criticism is quality control consistency — occasional reports of fit or finish problems appear, typically surface blemishes or minor dimensional variation rather than structural failures. For recreational use and home defense it's regarded as reliable. Competitors who put higher round counts through their rifles tend to move toward pricier forged lowers, though that reflects preference more than documented failures with Anderson's product.

Overall it fills its niche well: a complete, ready-to-build lower at a price that makes sense for a first build or a spare parts rifle.

I have used Anderson upper and lower receivers across more than forty builds without encountering a functional problem, so the basic quality has been remarkably consistent for me. This lower also fit a CDNN upper properly and made for a straightforward build. One pairing was less satisfying at the mating surfaces, where the fit with that particular upper was looser than I wanted. That experience convinced me that a matched upper and lower can be the better route when the tightest possible fit matters. Still, the receiver itself has proven dependable over many projects, and the generally clean quality keeps it among the parts I am comfortable building around.