The Aero Precision M4E1 Upper Receiver

The Aero Precision M4E1 Upper Receiver

Fantastic fit and finish. That’s exactly how I will start this mini review. I am updating my “modern” rifle to something that will help me in my marksmanship journey. I decided to try something new and about a year ago I pre-ordered a Vltor KMR but the length of time from the promised delivery date to when it actually hit the shelves was a long time between. I moved on and concentrated on High Power for a bit. So now I am back looking for an update to my rifle.

I decided to give the M4E1 a shot. I saw a few advantages to this receiver that intrigued me:

  • Simplified barrel nut / hand-guard system for quick assembly
  • Barrel nut is independent from the gas tube
  • If the hand-guard is damaged, it can be replaced by loosening 8 Torx bolts and swapping the rail

So for my DMR style re-build, I was willing to give it a shot. Right away I could tell I made a good choice. The fit and finish are peerless. The upper and hand-guard are smoothly anodized without defects and they interface with so much, damn me for saying it, precision. As you slide the hand-guard over the receiver it feels tight and secure without the bolts. The receiver has lots of real-estate to interface with the rail and it fits snug right away. The rail has anti-rotation tabs in addition to the torx screws that will keep it from rotating.  In case you haven’t realized it yet, the rail will not interface with all AR15s, as it needs a BAR style barrel nut if you want to adapt it to another “normal” upper.

AeroPrecision side view M4E1

The upper has some great machine work and the angular styling of the upper are not over-done. It’s a good looking piece of kit. The extended portion is the interface for the barrel and rail.

The installation process is simplified since there is no need to align a gas tube / barrel nut. Clamp the upper into a receiver block, insert barrel, slide barrel nut over barrel, torque in place with the included wrench, and then install gas tube and gas block. Once your done with that, slide the rail in place and screw it down. All done.

AP M4e1

A good sign when you cannot easily tell where the upper stops and the rail begins.

I assembled this upper with my old 20 inch barrel (which I will be replacing with an 18 inch barrel) just to have the gun assembled. I pulled the charging handle back and was happy to feel a really smooth pull without the grit you can find on some new upper receiver assemblies.  If you are lucky enough to have a suppressor it will accommodate up to 1.5″ diameter suppressors. I am not that lucky and do not have a suppressed SBR. ONE DAY.

Aero Precision M4E1

One thing to note: A negative of a upper assembly like this is the possibility of cross threading the screws. It should go without saying that care must be taken when installing the torx head screws. Strip a few out and your upper is done for. I had no problems and the bolts went in smoothly.

Aero Precision Full Rifle

I am satisfied, looks dang good.

I need to mention that Aero Precision is a site sponsor. Since this blog was launched (and then re-launched) i had been paying everything out of pocket. Gear reviews, junk I purchased for the blog, all of it was getting hairy on my finances so the nature of the beast is that sponsorship helps me out. That said, I purchased my M4E1 in full from Andrew at Reading Armament. This is not a freebie that Aero-Precision gave me in exchange for a favorable review and I am not beholden to AP for components as I re-build this weapon. My guns have all been parts guns, and they will be going forward.

I am very happy with the quality of my purchase and will recommend the M4E1 for anyone looking for a top quality upper / rail.

Written by lothaen


  1. Josh · December 15, 2014

    What length is the rail? It looks good with a FSB in the photo but I can’t get a good look at the end of it. Is there a noticeable gap between the front sight and the rail or does it all look good? I know that the final barrel length is you decision but just look at how cool that thing looks with the fixed sight and 20″ barrel!

  2. ERP · February 11, 2015

    The Aero M4E1 transformed that rifle brother! I just got my M4E1 a couple days ago. Absolutely love it. I built a .300blk pistol with it. The one thing I really like about the M4E1 is how tight it butts up against the receiver. The one weak spot on the AR15 platform was fixed by the Aero M4E1 and the M5E1.. Solid looking build brother.

  3. Sterling · February 23, 2016

    Just wanted to provide a little feedback with a recent experience.

    IMO I’ve had poor experience with this company. If you have a listed price on your site you should honor it. Recently they forgot to change a price and they told me it must be my “cache” that is not allowing the price to update. I thought this might be true but then I went back to the site and only 30 minutes after my email the price had been increased to the non-sale price.

    Here is the point…if my cache didn’t allow the page to update to the new price then how did it magically update 30 minutes after I sent an email saying I couldn’t get the listed sale price.

    It just speaks to the integrity of the company and unless otherwise corrected they have lost my business moving forward.

    • John · June 13, 2020

      Just wanted to add a reply concerning the caching comment above: you have to remember many times a broadband provider (Comcast, etc.), will have what is called TTL (time to live) caching set on their own severs to lower load. So it’s possible indeed, they changed the price, and you didn’t see it reflected on your side for a bit. It happens.

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