Finished my ultralight AR build (pics)

[Arizona_Mike]

The goal here was not to build the lightest possible AR, but the lightest practical and reliable AR. I ruled out anything but a steel slide lock/LRHO, flimsy minimal stocks, conventional polymer or magnesium lowers with a weak spot at the buffer tube mount, and aluminum bolt carriers.

It has been shot a few hundred rounds and seems accurate (lots of touching holes at 50yd). With the adjustable gas and low reciprocating mass, recoil feels no more than a standard AR and with less movement of point of aim.

I am very happy with the results. I was going for 4 1/4lb and almost made it.
Weight: 4.32lb (4lb 5oz)
As pictured (with optic, QD optic mount, 3-pt sling, QD sling hardware, QD Keymod mount, Houge grip): 5.22 lb (5lb 3.5oz)

LOWER:

• GWACS CAV15 MKII polymer lower receiver/stock
  • GWAS alumunim receiver pins
  • Nylon buttplate screws (will boil in black RIT dye in the future)
• Empty Carbine buffer (no slide weights)
• V7 aluminum mag release assembly and button
• V7 57-degree titanium-core ambi safety
• V7 aluminum buffer retainer pin

UPPER:

• Magtech magnesium upper receiver
  
  • Removed FA, polymer plug in hole
  • V7 aluminum dust cover
  • V7 aluminum dust cover rod
• BCM Gunfighter charging handle (standard)
• Boomfab Titane Titanium Bolt Carrier
• BCM Fluted 14.5" Mid Length Enhanced Lightweight (no handguard cap shoulder) Barrel, 0.625"
  
  • Adams Arms VooDoo Manimal thinwall A2 flash supressor (pinned and welded)
• Syrac Ordnance adjustable gas block, solid (0.625)
• BCM KMR10 10" magnesium handguard

Full resolution: https://dl.dropboxusercontent.com/u/21431738/guns/Ultralight/20141124_125240_5_cropped.jpg

Full resolution: https://dl.dropboxusercontent.com/u/21431738/guns/Ultralight/20141124_125336_6_cropped.jpg

Mike

 

[Armored farmer]

Nice job, man! Very well done.
I think you could put your name on that one and market it!

 

[Fishbed77]

Empty Carbine buffer (no slide weights)

Explain to me how this is working out for you. Not judging - just curious.

 

[strambo]

I believe it works due to the much lighter titanium bolt carrier. A mil-spec M16 steel carrier would be a rough ride w/o weights in the buffer!

 

[Field Tester]

Very interesting stock Mike. How does everything feel? Does it point naturally? How do you like it over all?

 

[tuj]

why did you choose an integrated stock/lower as opposed to an adjustable position stock? just curious.

 

[Arizona_Mike]

Slide weights are not needed in a semi auto gun. A few miliseconds of bounce can't cause out of battery fire when there is a disconnector. No semi-auto gun design uses them. I would not recommend going so light without an adjustable gas block. You could be severely overgassed.

It points very well. I did it as a challenge but I am going to carry it on hikes.

The integraded stock/lower with no buffer tube needed is tough. It is very thick where it needs to be and made of Nylon 6 (similar to a Glock). I would have to go to a polymer or magnesium lower and minimal stock to get as light or slightly lighter for a big decrease in durability. Conventional dimension polymer lowers have a reputation of breaking at the buffer tube mount point and I was unure about magnesium which is significantly more brittle than aluminum.. Also minimal stock are less comfortable and of questionable durability.

The V7 parts are not expensive compared to conventional parts but the barrel, handguard, and especially bolt carrier are very expensive. Probably not viable as a commercial package.

Posting on my phone. Did I cover all the questions?

Mike

 

[urbaneruralite]

Slick. Now do a 6.5 Grendel with 20" and Ace stock so I can copy it.

 

[Jackal]

The mismatched upper/lower colors remind me of a Scar.

 

[Arizona_Mike]

The mismatched upper/lower colors remind me of a Scar.

Unfortunately FDE is the Khaki* of the gun world. Upper is Cerrekote FDE (the dust cover is very close but slightly creamy) and lower is designed to match Magpul FDE which has more green.

*-a Hindustani word meaning "dirt-colored"

Mike

 

[1KPerDay]

Very cool.

 

[chicharrones]

A very interesting AR build!

 

[horsemen61]

I like it !

 

[Armored farmer]

Yea, the light weight is appealing for my 50yo legs.

 

[rottdogsparky]

What would it cost to build your rifle and what did U spend?

 

[Arizona_Mike]

What would it cost to build your rifle and what did U spend?

I'm afraid to add it all up. I built this more as a challange to myself to get as light as I could and still be useful and ended up with something (unexpectedly) I plan to carry on hikes, etc.

If you look at some of my plannnig threads (and my comments on Taliv's ultralight thread) I included some costs. Interestingly I concluded over a wide range of part types that the differential cost increase for going light was about $90/oz.

Mike

 

[justice06rr]

Pretty good build. An AR under 5lbs is definitely a lightweight, and is probably very easy to hold and shoot.

Any reason why red dot is so far back though?

 

[Arizona_Mike]

Having the red dot just in front of the eye gives an excellent field of view and does not block the line of sight of the opposite eye. What little is blocked for the main eve is way out of focus and mostly covered by the opposite eye. I've tried both near and far and it always comes back to personal preference.

Mike

 

[Arizona_Mike]

Just an update, I have carried this on several hikes in pretty rugged terrain and absolutely love it. The outside of the FS has gotten a little dinged up on rocks but the inner edge is untouched.

I appreciated the shortness and light weight on this hike up a Mesa in the Weaver Mountains west of Prescott. I was forcing my way through brush most of the way and there were lots of boulder fields to cross.
View from road:
https://dl.dropboxusercontent.com/u/21431738/130005 - Clean.jpg
2/3 up looking down: https://dl.dropboxusercontent.com/u/21431738/163022 - Clean.jpg

Mike

 

[MachIVshooter]

You did well on the weight. Good job.

Having said that, I cannot stand the Cav arms monolithic lowers. Just plain hideous to me.

 

[d2wing]

I like it. Interesting solutions. Thanks for sharing.

 

[Arizona_Mike]

I am debating shedding almost another oz with the new Ti barrel nut available for this rail. It's well under the $90/oz cost ROI that parts so far averaged. The Ti barrel nut clamps will save less than 1/5th ounce for $35--definitely not worth it!

Mike