My first experience with Aero Precision came about 10 years ago in the form of a stripped lower.  The build went well and the lower was a breadcrumb on the trail to more parts from Aero.  As a gun shop owner, when customers were looking for quality parts at a price that wouldn’t break the bank, Aero was often the recommendation.

When given a shot at reviewing an Aero upper receiver , I chose the M4E1 upper with a 16″ 300 BLK barrel (1/7″ twist) and a  keymod rail.  The “E” in the name is for enhanced.  The area specifically being described here is the handguard and barrel mounting system.  The handguard mounting system and upper receiver are part of the same forging, making it an ultra-strong setup that is likewise simple.  One can slide his barrel assembly into the upper, tighten using the included wrench, then toss on the rail and button it all up with eight screws.  It’s easy, solid and makes for a nice and light upper.  This system works not only with Aero precision’s handguards, but also most BAR system handguards.

Aero Precision M4E1 Upper | Review
Photo by Rex Nanorum

I took the M4E1 out to the range with a  couple hundred rounds to use.  I had five different loads available, all pictured below.  Ranging from 90 grains to 220 grains, this is a nice variety of rounds with which to test accuracy.  The M4E1 was a snug fit in all three lower receivers I own, but too snug in the lower that contains a match trigger.  (Side note, that lower seems to be a little out of spec, not fitting right with ANY of the uppers I’ve put on it.  Not Aero’s fault here.)  So, the day’s testing was to be done at 100 yards with a stock mil-spec trigger.  Given a 1-turn-in-7-inch barrel, this usually means the gun will favor the mid weight and heavier bullets.  On to the shooting.

Aero Precision M4E1 Upper | Review
The day’s variety. Photo by Rex Nanorum

Looking through a boresighted Leupold 1-6x Vari-X VI, I gave a quick three round zero using Remington’s 115 grain UMC.  I worked 5 round groups with each ammo type, here are the results from most accurate to least.

  1.   Barnes Range AR 90 grains.  The bottom 4 rounds were touching.  The little guy up top?  I wouldn’t worry about that little guy.  That was a called flyer, I went a bit spastic on the trigger pull.
    Photo by Rex Nanorum
    Best group of the day.  Photo by Rex Nanorum
  2.   Remington UMC 220 grain subsonic.  Averaged just under 1.5″ groups.
  3.   Barnes 110 grain Tac-TX.  Averaged just over 1.5″ groups
  4.   Remington UMC 115 grain.  Between 1.5″ and 2″ groups
  5.  Gorilla 208 grain.  These groups resembled shotgun patterns.  This is normally a pretty accurate round out of other 300 BLK uppers, it simply didn’t agree with the M4E1.
Aero Precision M4E1 Upper | Review
Whaaa? 208’s from Gorilla didn’t play nice in this upper. Photo by Rex Nanorum

I’ll note I’ve never been uber proficient at nice tight groups.  I’ve always been far more successful at speed shooting, so I dialed the Leupold back to 3x and spent the rest of the day shooting and transitioning back and forth across the range.  Despite a generous 1.8″ inside diameter on the keymod rail (as to allow suppressors to tuck underneath them), this is a light and responsive upper.  Having forgotten my weapons lube in my other range bag, some 10w30 motor oil kept the BCG running smooth and reliably.

Despite my challenges keeping the groups as tight as I would like, I had no troubles banging various sized targets from 50 to 300 yards with speed.  Towards the end of the day I had really begun to realize this upper is capable of much better accuracy than I am.  The M4E1 is light, rigid and speaks of quality at every turn.  At $460 from, this is an upper I’ll recommend.  Once I get another range trip (and some practice) in, I’ll update with more accuracy results.

This article courtesy of Rex Nanorum from The Loadout Room.