Today we’re continuing our journey through the ultralight AR15 build, covering the lower receiver, version 2.0. The upper receiver article is covered here, while the full rifle article is coming next. To recap, originally I wanted to build a tough, accurate rifle that came in under 6lbs, with the suppressor and optic included in that weight. Version 1.0 came in at 5.776 lbs, but there was still far too much fat on the rifle for me to stop there. So my new goal is for the rifle to be sub-4lbs, before suppressor and optic. This build is for over the counter parts only, none are drilled out or modified by me. Given that the end goal for this rifle is one that is extremely durable, I have forgone the use of polymer receivers and carbon fiber forends/stocks. I don’t doubt there are instances where those can be tough, but they don’t have the same track record as good ol’ metals.
Given that the lower hasn’t changed as much in version 2.0 as the upper has, below are the new items followed by a quick recap of all the parts involved, by the manufacturer.
MA Parts Inc.
CAR-15 stock body 4.7oz $25
It’s not easy to find something lighter than the MFT’s Minimalist stock, while still maintaining adjustability. I know there are “end cap” stocks out there that simply affix to the end of the buffer tube/receiver extension, but I’d like to keep the option to adjust the stock for a heavier coat, gear, body armor etc. This drops a little over an ounce off the MFT, while sacrificing no functionality. Spray painted to match its permanent host rifle.
Taccom 3G Carbine Recoil System 1.1oz $22.95
An interesting weight dropper, Taccom’s buffer setup replaces the standard buffer with a lightweight, two piece synthetic setup. For use with standard BCG’s or lightweight BCG’s, this package requires an adjustable gas setup to perform. Uses a standard recoil spring (not included). Tune your system with less reciprocating mass and you can still have excellent reliability and get your weight savings.
V Seven Weapons Systems:
- 2055 Lithium-Aluminum Lower 6.4oz $359 Review
- Titanium QD Endplate 7.2g $32
- Ultralight Bolt Catch S7 steel 9.0g $31
- Titanium Trigger/Hammer pins 2.35g $17
- 57° safety lever w/Ti core 8.3g $49
- 11 position 2055 Alloy Buffer Tube 3.28oz $79 Review
- Ti Buffer Retaining Pin 1.1g $7
- Lightweight Castle Nut 6.7g $22
- Ultralight Mag Catch/Release 4.9g $30
V Seven has obviously contributed mightily to this project. Their work with titanium and 2055 lithium-aluminum alloys has made this project (and many like it) possible. There’s not much weight I can shave here. I am looking into magnesium receivers, but want to see if the “kaboom” issue has been fixed before I touch that with a 10 foot pole.
- Extended takedown pin set 1.3oz $12 Review
While these pins are nice, they’re a luxury item on an ultralight build and need to be replaced. I can drop nearly a full ounce here, which is nuts considering the part we’re talking about. V Seven’s extended titanium pins have a similar profile but come in at only 8.6 grams. Standard profile titanium pins from V Seven are 8 grams flat.
- Super Semi-Auto Trigger 2.1oz $240
Chosen for accuracy (and availability, I won this in a FB giveaway), this is one of the lightest premium triggers out there. There’s a couple skeletonized triggers that are barely lighter.
Read Next: Ultralight AR-15 Build Part 2 | The Upper
Mission First Tactical:
- Engage Tactical Pistol Grip 2.12oz $19.99
The only lighter option I can find online (but not verify) is the Magpul K Gen 1, which is .1oz lighter.
Assorted Mil-spec parts
- Buffer Spring 1.9oz $7
- Grip Screw 8g $2.50
I haven’t seen any ways to reduce buffer spring weight without compromising reliability. The grip screw can still be replaced with a titanium one, dropping 5 grams. Again, see V Seven.
So as it is, the completed lower is at 1.517 lbs or 24.27 oz. Cost for this lower as shown is $955.44. It’s worth noting a good portion of that is in the premium trigger from Geisselle, which was selected for it’s accuracy enhancing potential rather than it’s weight. This comes out to $39.37/ounce. With a mil-spec trigger, it’s around $720, and under $29.50/ounce.
With the upper and lower completed, it’s range time! I’ll be using a magnified optic for accuracy testing and will continue to make any small tweaks and improvements I can before the final countdown on this ultralight AR15!
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