Aero M4E1 Raw

X15 Vs M4E1 Lower Receiver

The lower receiver is the registered portion of the AR15 that houses many critical components such as the fire control group and buffer assembly. This is generally the part you will want to start with when building an AR15.

Aero Precision offers two lines of AR15 pattern lower receivers, the X15/Gen 2 Lower Receiver and M4E1 Lower Receiver.

X15/AR15 Gen 2 Lower Receiver Details

Our X15/AR15 Gen 2 Lower Receiver is very similar to what you would expect from a mil-spec AR15 Lower Receiver, with a few added features to help with assembly and use of the firearm you intend to build.

The first thing to point out is that our AR15 Gen 2 lowers have an increased magwell flare, allowing for easier insertion of magazines compared to standard mil-spec lowers.

Our AR15 Gen 2 Lower receivers include a nylon tipped tension set screw threaded into the lower receiver, located adjacent to the grip screw threads. This allows the end user to tighten it down to the desired fit, removing any slop between the upper and lower receivers when they are mated together. Although we see very nice fitment between our upper and lower receivers, this is a great feature when our lower receiver is being used with other manufacturer’s upper receivers.

At the very rear of the receiver, we thread our takedown pin detent holes to accept a 4-40 set screw. This allows the builder to install these parts independently of the buffer assembly and avoids headache and frustration when trying to keep the detent spring compressed while threading the end plate and castle nut onto the buffer tube. The 4-40 set screw is not included with the lower receiver, but it does come with most of our AR15 Lower Parts Kits.

M4E1 Lower Receiver Details

The M4E1 Lower Receiver is a forged lower we produce that offers many of the same benefits and sleek aesthetics of a billet lower receiver, while maintaining the integrity of a forged lower all at a great price!

M4E1 Lower Receivers

The M4E1 Lower Receiver shares the tension screw as well as the 4-40 set screw features that are found on our Gen 2 Lower Receivers.

The magwell on the M4E1 has a more extreme flare than that found on the Gen 2 Lower Receivers.

The M4E1 Lower Receiver also features a built-in trigger guard. The trigger guard is enlarged and allows for easier shooting when using gloves.

We have replaced the traditional roll pin used to attach the bolt catch to the receiver with a threaded pin. This simplifies the build process by removing the need for special punches, requiring only a 1/16” hex key. This installation method also minimizes risk of damaging your lower receivers finish when installing the bolt catch. This threaded roll pin is included with the lower receiver.

Lastly, the M4E1 features selector markings that accommodate both traditional 90-degree selectors, as well as 45-degree selectors depending on which style you prefer.

X15 VS M4E1 Lower Receiver

Comments (2):

  1. William berry

    June 14, 2023 at 12:42 pm

    Very informative, thank you .I would like to see more of this type of informative content.

  2. Peter

    July 5, 2023 at 2:40 pm

    Good information for novices


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