With the ever advancing march of machining technology bringing us lighter and stronger parts made from exotic materials, it has been recently popular for writers to detail their efforts to construct a lightweight AR-15.  All of these AR build articles start with a mission statement; some aiming for a sub-4 lb rifle, some for a certain weight within a certain budget.

My goal is simple: Constructing a lightweight AR rifle that is under 6 lbs-with suppressor and optic-without sacrificing durability or reliability for weight.  I want this to be a fantastically tough field rifle, just one that’s more suited for a scout rather than a fixed support-by-fire position.  There are parts out there that are lighter and there are parts out there that are cheaper.  While I’m not averse to using premium cost parts that are full-strength, if there is a cheaper option I feel has the same impervious nature, then I’ll use it.  This build will place emphasis on parts I’ve used in reviews before (I already have them on hand).

So without further ado, below is what I have put into the lower receiver thus far, sorted by manufacturer.

Mission First Tactical:

Lightweight AR Build | Part 1- The Lower Lightweight AR Build | Part 1- The Lower Lightweight AR Build | Part 1- The Lower

The Minimalist is one of the most oft used stocks for lightweight builds, which seems obvious given it’s incredibly svelte figure.  While I could have saved 1.2oz using the old CAR-15 buttstock I had lying around, the MFT stock is far more comfortable, durable and lacks any wobble.  The Engage V2 grip is very comfortable, especially when used with the stock collapsed close to the receiver.  The grip is also .08oz lighter than advertised, which is nice when every gram counts.  The SCMP556 mag is another competitor in the “over-engineered polymer mag” market.  Four-way anti-tilt follower, stainless steel spring, dot matrix for paint pens and more.  Beefcake.

V Seven Weapons Systems:

Lightweight AR Build | Part 1- The Lower Lightweight AR Build | Part 1- The Lower Lightweight AR Build | Part 1- The Lower Lightweight AR Build | Part 1- The Lower Lightweight AR Build | Part 1- The Lower Lightweight AR Build | Part 1- The Lower

V Seven is awesome and you’ll see their products in many lightweight or premium builds.  Their 2055 Lithium-Aluminum alloy is a big improvement in what we can expect out of aluminum.  Lighter, stronger, more rigid and with a greater corrosion resistance than 7075 T6 aluminum, this alloy shows what’s possible when advanced metallurgy meets firearm design.  Almost all of V Seven’s parts are being made with titanium, 2055 alloy or a lightweight, redesigned profile.  In numerical terms, these parts come in at 30-62% lighter (and usually stronger) than their mil-spec steel counterparts.  While it may seem like an unnecessary expense to take a steel part that weighs a few grams and cut that weight in half, the effect is cumulative and quickly adds up.  In a few cases, the upgraded part is only a few bucks more than the standard.

Small details are never overlooked at V Seven, from opportunities to shave an ounce to opportunities to make mechanical improvements.  Such is the case with the buffer tube and the mag release button.  The former features 11 positions, detent lock and drain holes, while the latter features a fantastic diamond-pattern face.  The 57° spin on the safety lever is a more comfortable, faster throw to get your gun going.

Xtreme Precision

Lightweight AR Build | Part 1- The Lower

I reviewed these pins a while back and found them to be a nice little addition to the lower. About half of the builds I’ve done had a really tight upper-to-lower fit and these help make takedown a snap.

Geissele Automatics

Lightweight AR Build | Part 1- The Lower

Ultralight AR-15 version 2.0 |  1 pound lower (part 2)

Read Next: Ultralight AR-15 version 2.0 | 1 pound lower (part 2)

Easily one of the most noticeable improvements over a stock AR, I was lucky enough to get one of these drop in trigger assemblies from Geissele in a Facebook giveaway.  The two stage trigger comes in at 4.5lb total pull-weight and is as crisp as a combat trigger can get.  Geissele is well-known for their excellent triggers, with good reason.  This one has obviously been painted a couple of times.

Assorted  Mil-spec parts

  • Standard Weight Buffer                       2.95oz               $15
  • Buffer Spring                                          1.9oz                  $7
  • Grip Screw                                                 8g                    $2.50

I don’t know who made these or how much they cost, they came out of my spare parts box.  I’ll use Brownells as a cost reference for these.

While most of these parts should work under any condition, I’ll reserve the right to change them out (and update cost/weight in future articles) if something like the buffer needs to be adjusted to work with a lightweight BCG.

The completed lower weighed in at 1lb 11.3oz or 1.7lbs and comes in at a cost of about $982.48. That’s ~$36/oz.  These tabulations are without the empty mag for now.

So yes, this is an expensive lower, but I’m looking for heirloom level durability.  2055 alloy and titanium are right up my alley with their strength and resistance to the elements.  I’ve started the layout for the upper and am currently searching around for parts availability.  Stick with me as I lay out the upper plan, then test the whole rifle for accuracy and reliability.

Stay tuned…

(Note: just before publication I received word from Taccom that I’ll be receiving their ultra-lightweight recoil system.  Approx 1.2oz total weight.)