You mounted your optic very low?  That's crazy light.  Under 4 lbs canless?

Here's my latest.     Wasn't specifically built as an ultra-light, but it certainly qualifies.   14.7 Ballistic Advantage pencil with FSB (pretty thick for a 'pencil, IMHO), pinned and welded nitride A2 flash-hider, Aero M4E1 receiver set, Aero enhanced buffer tube kit, Larue MBT-2S trigger, CMMG LPK, Magpul grip, UnbrandedAR mil-spec+QD stock, SI port door (because I like them, not for weight).     With sights, it comes in at 5.78lbs (though in reality, once I stick a red dot, a flashlight, sling, etc on it - it'll be over 6 the way I'll run it).

I am really happy with how this one turned out.   Not only is it lightweight, but with the 14.7+mid-length gas and my natural hand position right behind the front sight base, leaves very little weight extending past my support hand - makes the gun feel very nimble and quick pointing.  

Nice!  Mid-gas 14.7" looks like it's long enough to take a bayonet, even though I know it's not.  Probably good enough for a rifle grenade.  Thanks for the tip on the Unbranded AR stock, will have to get one for my Fold-AR build.

Yeah, I've been using those UAR stocks for a while now.   The weight has varied somewhat over the years, but if you pull the sling swivel from the Unbranded AR stock, it comes in between 5.9 and 6.1 oz, and is like $13-$14.    And it has QD - best bang for the buck stock on the market, IMHO.

OK, here we go, this one is getting pretty crazy-light for a "real world useful" gun.    4 lbs, 15.3 ounces, INCLUDING OPTIC AND BUIS!!   All aluminum and steel (and a bit of Ti here and there), with forward-assist, with port door, with all the trimmings of a 'real gun'.  

Run-down

Mainest-thing for weight loss - a 14.5 Faxon Match pencil barrel (with 3 prong Faxon flash-hider pinned and welded)  (19.4oz all-in)  (haven't shot it yet, but the borescope says this is easily the cleanest/smoothest/nicest looking rifling I've seen on any of my Faxon's, chamber looks good, leade looks good, crown looks good, etc - so I'm expecting it to at least be "pretty good", and possibly "OMG, you shot that group with a PENCIL barrel?" accurate).    

Faxon upper (6.98 oz - was bummed, should have been 6.88)
Magpul port door (.3oz)
SI forward assist (.35oz)
Aero Precision S-One 9.3 handguard
Wojtek Weaponry .625 gas block
DSArms lightweight Nitride BCG (9.14oz)
Holosun 403b in a Sig Sauer Romeo MSR mount (4.2oz all in)
Magpul flip up front sight (v3) (0.88 oz) (the red dot if it fails, becomes the ghost ring for the front sight - a setup which works remarkably well actually).

Lower is an older (and lighter than current series) Aero M4E1, mostly mil-spec except for the Ti 2A Armament takedown pins, aluminum 2A Armament castle nut and end plate, and PSA fluted buffer tube, and a V7 Ti grip screw.    Added an old-school CAR stock (4.2oz), and there she be.

To be fair - the castle nut is 6061, which is the one and only piece of this that would make me think "hmmm, might should have gone with something tougher there if I was gonna pack this for a SHTF gun", so I'm going to replace it with a steel one (which will put the gun at 5.0lbs even).   Also a footnote, those with super-sharp eyes will see that the gas block is on backwards and there is no gas tube - long story about my idiocy I'll spare you, but the new gas tube should be here soon - so between the gas tube and castle nut, I bet it's probably 5lbs 0.5oz in the truly final configuration.

Anyway, here be the pics.

Nice!

Gonna try to break 6 w/ a 20" H&R bbl and pure polymer upper.

That sounds very doable.   I got a 20" lightweight barrel from JSE Surplus (it's a .625 gas block, but seems a little chunkier than a full pencil, IMHO - 1.8lbs on the scale - I assume the H&R barrel is similar if not a touch lighter) that is right there.  And mine didn't use a poly upper or nothing - a 15 inch Aero S-One handguard on an M4E1 upper.   Ready to go bang upper weighs 3lbs 13.5 oz.   A fairly mil-spec lower with a light-ish weight stock on it (waffle stock minus the sling swivel, MFT minimalist, etc) comes in at a hair under 2lbs.   So without sights, mine sits at 5.84lbs.    You could easily loose 2oz off the upper from my build just by using a no-FA upper with a lightweight port door.   Could loose another 1/2 oz on the muzzle device by using like a MFT 3 prong comp or VDI Manimal flash hider.     That would leave you 5oz for an optic.   Take another 1/2oz of the lower (lightweight takedown pins and end plate would do that easily), and you could simply drop a Romeo 5 on it and come in under the 6lb mark.

If you go back to near the end of the previous page, I got an 18" Faxon barrel gun with a 3x Burris prisim on it that comes in at 5.8-something lbs (and that's a 9oz scope).

I appreciate the thorough breakdown you posted here.

FYI…the typical gun safe restriction is volume, not weight…HaHaHa!

She looks a little rough on the outside, but the inside is solid.  I reduced cost slightly by Frankensteining a cheap handguard, charging handle, and mid-tier upper receiver.

Weight: 4 lbs 6.6 oz

For me, this is light enough.  And it could easily take a set of BUIS, a lightweight ambi charging handle, and a compact light & laser combo and stay under 5 lbs.


I made up a nice BB code table of all my parts, weights, etc., but because mine is a "new account," that table is WAY longer than what I'm allowed to post.  
So, maybe in the future...?  :shrug:

Very nice.  Really like the stock & the shaved handguard.  Until you have 50 posts or so, there's a maximum character limit.  Maybe you could break up your table into categories & make multiple posts?  Or just post the text?  Up to you.

ARFCOM's been burned before by folks who sign up w/ multiple accounts & spam the site (sometimes w/ dick pics), hence the temporary restrictions on noobs.

Ok, this I can do.
                                                                                                                                                                                                                               

UPPER GROUP(pt1)		LBS		OZ		ITEM NAME	DETAILS
Upper Receiver	Aero Precision	0		6.2		Forged receiver, no FA	No FA.  Manually enlightened. Fatigued (cosmetic).  Weighed.
Charging Handle	Davidson Defense	0		1.1		Mil spec carry handle	Manually enlightened.  Fatigued (cosmetic).  Weighed.
Dust Cover	Strike Industries	0		0.4		Enhanced Ultimate Dust Cover	Black, weighed.
Bolt Carrier Group	2A Armament	0		5.9		Titanium Regulated Bolt Carrier	AR15, Black. weighed
-- Firing Pin	V Seven					Titanium Firing Pin
Barrel Nut	2A Armament	0		1.0		BL Aluminum Barrel Nut	Modified, weighed.
Barrel	Faxon	1		5.6		5.56 Gunner 14.5"/16" w/ integrated brake	Weighed.

                                                                                                                                                                                                                                                                                               

UPPER GROUP(pt2)		LBS		OZ		ITEM NAME	DETAILS
Hand Guard	Lakota Ops	0		6.5		Lightweight FF Rail 10"	Manually enlightened.  Fatigued (cosmetic).  Weighed.
-- Rail Covers 1	Vism	0		0.4		M-Lok Rail Covers	Weighed.
-- Rail Covers 2	Strike Industries	0		0.3		Bikini Finger Stop
-- Rail Covers 3	UTG	0		1.4		Ultra Slim M-LOK Vertical Foregrip	Fatigued (cosmetic).
-- Gas Block	Samson	0		0.6		.625 lightweight Gas block
-- Gas Tube	Trybe Defense	0		0.6		Mid length gas tube	Weighed.
Optic 1	Vortex	0		1.1		Venom Red Dot
Optic 1 Mount	Leapers UTG	0		1.5		Super Slim RDM20 Mount
	UPPER WEIGHT:	3	lbs	0.7	oz

                                                                                                                                                                                                                                                                                                                                                               

LOWER GROUP (pt 1)
Stock	Wilson Combat					Buffer Tube / Stock Combo	Weight included in buffer extension tube.
-- Stock Accessory 1	Fortis			0.4		QD M-LOK Sling Mount	approximated weight
-- Buffer Extension Tube	Wilson Combat			5.2		Buffer Tube / Stock Combo	Wilson Combat branded version of Smoke Composites tube/stock. Weighed
-- Castle Nut	Fortis			0.2		Al Standard Castle Nut	Weighed
-- End Plate	Fortis			0.2		QD Al endplate	Weighed
-- Buffer Spring	Spring Co.			1.7		Tactical Red Extra Power Spring	Weighed
-- Buffer	Davidson Defense			0.9		standard carbine	emptied, weighed
-- Castle Nut	Fortis			0.2		Al Standard Castle Nut	Weighed
-- End Plate	Fortis			0.2		QD Al endplate	Weighed
-- Buffer Spring	Spring Co.			1.7		Tactical Red Extra Power Spring	Weighed

                                                                                                                                                                                                                                                               

LOWER GROUP (pt 2)
-- Buffer	Davidson Defense			0.9		standard carbine	emptied, weighed
Lower Receiver	2A Armament			7.2		Palouse Lite Forged Receiver	Weighed
Pivot & Takedown Pins	Strike Industries			0.2		Ultra Light Pivot/Takedown Pins	Weighed
Safety	V Seven			0.3		Ti RH	Weighed
Pistol Grip	Tactical Link			2.2		PDW Grip	Weighed
-- Pistol Grip Screw	Fastener-Express.com			0.1		Al Socket Head Cap Screw	1/4"x28x3/4"
Trigger Guard	BCM			0.2		Polymer trigger guard	Weighed

                                                                                                                                                                                                                                                               

LOWER GROUP (pt 3)
FIRE CONTROL GROUP				2.3
-- Trigger Assembly	Geissele					G2S	Weighed
Bolt Catch	V Seven			0.4		Ultra Light S7 Tool Steel Bolt Catch	Weighed
-- Bolt Catch Spring & Plunger	various			0.0			Weighed
Mag Release Assembly	2A Armament			0.2		AL Mag Catch Assembly	Groove, weighed
	LOWER WEIGHT	1	lbs	5.9	oz
TOTAL	Weight	4	lbs	6.6	oz

That's it.  I have a version of this with MSRP of each too, but I had enough fun paring down and parsing this up.  Total MSRP is around $2325.  (I didn't track what I paid for each part, but I was patient and hit a lot of sales.)

And, thanks for the compliment on the build.  I appreciate it.

If something appears to be missing, I might have chopped it off when editing this up.
Oh--no worry on dick picks here -- keymod makes me uncomfortable.

Bravo Zulu.  Nicely done, thank you.

Anyone remember where to get polymer buffer tube? I'm not finding it.

5.87 pounds with 11.5 length of pull.

Been a long time, but I got mine out of a budget outfit in Arizona.  Last time I checked, think their website was down.

"Economic" LW 16" build. Focus was on parts on sale or from the used market, and keeping it at or under 6lbs.

Sitting at 5lbs 15.5 oz.

Titanium RCA BCG, factory Aero pencil upper.

SLR 1.93 1.4oz mount.

Clean chop on the kp15 .

nice

bought my kp-15 lower, threw a couple of my uppers on it just for fun to weigh, I have a 16" m4 profile barrel upper with that same hg and magpul buis.  was shocked how much lighter it was.  balance is off, cg moves well forward of the front of the magwell.  planning to do another Dolos takedown upper with lightweight barrel assemblies for it.  The Dolos kit will only add a few ounces.  first barrel will be a Wilson 300HAMR lightweight profile and Brigand Arms Edge carbon hg.

Here's my Cola Warrior prize table, built for everyday use, fairly lightweight, mostly aluminum and not plastic, AR-15.
Cola related parts include the SOLGW Cola branded lower, Geissele SSA-E trigger, an ALG EMR V1 12" rail from Cola West II, and an Arson Machine Co. MLOK QD sling mount on the rail.
Red dot is a SIG Romeo 5 in a factory mount.
Flashhider is an old steel Gemtech Bi-lock so I can run my Gemtech suppressors... it's not particularly light, but it is lighter than the newer versions.
The barrel is a 16" Ballistic Advantage pencil profile midlength in .223 Wylde with their factory gas block... it's pretty light.
This rail came off the prize table at my very first Cola Warrior which was held in Reno, NV... it's very light and handy with lots of MLOK mounting points.
This 12" ALG EMR V1 has a Cola Warrior marked Arson Machine Co. MLOCK QD mount out front from the prize table at Cola Northwest.
The upper is a lightweight DSA that, while light, has unsatisfactory tolerances and required shimming for an appropriate barrel fit... it's light but I can't recommend it.
Charging handle is a Radian Raptor LT... and like everything Radian it is very well made and it's also pretty light.
Polymer dust cover is from Strike Industries... very light and easy to install.
Forward assist is also from Strike Industries and was something I had sitting in the parts bin... not particularly light, and a forward assist is certainly not necessary on this build. In retrospect, a lightweight upper without a forward assist would have been the smart move but I got the upper for a deal and sort of on a whim.  Oh well...
The biggest, and most expensive, weight saving component is the 2A Armament regulated, titanium bolt carrier... crazy light, easily adjustable, outstanding quality.  Very impressed.
The bolt is a nitrided Faxon that was sitting in the parts bin... not sure if there are any reliable lightweight options when it comes to AR bolts.  This Faxon bolt seems to be of decent quality and average weight.
The lower is a run of the mill Cola Warrior branded SOLGW forged lower... not a lightweight lower by any means, just a quality forging with a fantastic rollmark.
Trigger is a Geissele SSA-E from a Cola fundraiser for a fellow Cola Warrior who was facing a medical crisis... fantastic trigger as usual from Geissele, and the serial number matches the serial number on my Cola lower, so that's kinda cool.
No clue on the manufacturers of the aluminum receiver extension or steel castle nut but the end plate is an IWC QD sling mount... just random, regular weight stuff from the parts bin and I could probably shed some weight here without sacrificing strength or reliability. I do trust the IWC QD mount though so I would probably keep it on this rifle.
Buffer is a generic carbine buffer with nothing in the tube, all weights removed... weighs one ounce and can't get any lighter.
Recoil spring is a red Sprinco... it's recommended by 2A Armament for use with their adjustable titanium bolt carrier and an empty buffer.
Pistol grip is a Magpul MOE with a steel screw and the stock is a Magpul MOE SL-K with a Magpul QD MLOK on it... these are just reliable parts that are on the lighter end of the spectrum but not specifically manufactured in the pursuit of weight savings.
Not sure of the manufacturer on the ambi safety but it's steel and works as it should... I could certainly save some weight here I bet.
Trigger guard is your typical Magpul aluminum model and all the other lower parts like the mag release, take down/pivot pins, bolt release, misc pins, etc. are your generic steel or aluminum items... going to titanium  on most of these should save a bit of weight at a serious hit to my wallet.

So I think that about covers it...
And the weight as shown comes out to... 5 pounds 9.75 ounces.
I think it's pretty good for a mostly aluminum AR with dot... and built with parts I would trust to take a beating and run reliably for a very long time.  

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well, I went cheap when I found the upper receivers I bought were on the tight side and a Dolos takedown wasn't going to work, so a surplus Bushmaster pencil barrel, Aero upper, MagPul SL hg, and cheapie Tacfire 1-4 lpvo got it to balance within the magwell.  

5lb 8.1oz without the scope and mount.  scope and mount are 1lb 3.5oz.

still working on picture hosting - but one KP-15 with a standard upper, pencil barrel, and MagPul SL hg looks pretty much like another...

I have some goals, gentlemen

Get your wallet ready 😁

That looks awesome!  You could shave at least an ounce by swapping the pistol grip with the Hogue 15 degree!

My build is basically going to be the same thing except a slightly shorter barrel, railed handguard, lo pro gas block, SF4p, and no FA on the upper.

My latest build came in at about 5.7 lbs with the stock installed & a 14.4 oz Toolcraft BCG. I have since replaced that with a PSA premium to save a couple ounces.
I have added a PA 5x micro prism & PA red dot w/piggyback mount, TLR RM1 & SOCOM MINI2 can

Specs below. Next build, I want to try to get it much closer to 5 lbs before accessories.

Ruger stripped lower
B5 Type 23 grip
Geissele ambi safety
Stag LPK
V7 takedown pins, grip screw, ejection port cover & rod & end plate & castle nut
Centurion 14.5" lightweight hammer forged barrel
Magpul enhanced trigger guard
Toolcraft BCG
Warhammer CH
B5 Bravo stock
Centurion rail covers
Slate hand stop
Odin works extended mag release
CMMG Zeroed bolt catch
Larue MBT-2S trigger
2A Armament upper receiver
2A builder series buffer tube
Midwest micro gas block
Centurion gas tube
Strike FA
Geissele Super 42 H2 buffer & spring
Midwest 12.6" Ultralight handguard
Surefire closed tine FH/suppressor adapter

Post pics of that up here:

https://www.ar15.com/forums/ar-15/ULTRA_light_weight_picture_thread____the_under_6_crowd_/118-625051/

My latest build came in at about 5.7 lbs with the stock installed & a 14.4 oz Toolcraft BCG. I have since replaced that with a PSA premium to save a couple ounces.
I have added a PA 5x micro prism & PA red dot w/piggyback mount, TLR RM1 & SOCOM MINI2 can

Specs below. Next build, I want to try to get it much closer to 5 lbs before accessories.

Ruger stripped lower
B5 Type 23 grip
Geissele ambi safety
Stag LPK
V7 takedown pins, grip screw, ejection port cover & rod & end plate & castle nut
Centurion 14.5" lightweight hammer forged barrel
Magpul enhanced trigger guard
Toolcraft BCG
Warhammer CH
B5 Bravo stock
Centurion rail covers
Slate hand stop
Odin works extended mag release
CMMG Zeroed bolt catch
Larue MBT-2S trigger
2A Armament upper receiver
2A builder series buffer tube
Midwest micro gas block
Centurion gas tube
Strike FA
Geissele Super 42 H2 buffer & spring
Midwest 12.6" Ultralight handguard
Surefire closed tine FH/suppressor adapter

PHOTO

I hope this build makes sense to other people but I'm pretty happy with how it turned out. My goal was to build a "duty" rifle that met the thread requirements. I don't like how imprecise that term is but for me it meant: red dot, no BUIS necessary, sling, light, full-weight M16 BCG, H or H2 buffer, handguard that extends past the gas block and no ugly parts. Yes, that's pretty subjective but I hate the look of skeletonized grips and handguards and any receiver set that's radically different from normal forged.

Current weight: 95.6 oz with H buffer

Lower:
APC M16-cut lower with standard LPK and receiver extension
Magpul K2 grip
Damage Industries waffle stock with QD mount
H1 buffer

Upper:
Aero forged without FA
Brownells slickside chrome BCG
Faxon pencil barrel with slim integral flash hider
Midwest Industries 12.6 ultralight rail with titanium barrel nut
Holosun 403B with included 1/3 cowitness mount
Surefire M140A light
Manta rail covers

Vickers sling

---
Replacing the K2 with a B5 grip should save a fraction of an ounce. If anyone knows of a slightly lighter Aimpoint Micro footprint mount (currently 1.3 oz), I might try that as well but I didn't see anything in the parts weight database.
I want to test with an H2 buffer but that takes it to 96.5 oz. Removing the rail covers would probably get it back below 6 lbs in that case but I'd rather not. Sticking with the H buffer might be the way to go.

The current iteration of Lightweight Project 2.0.  This rifle will cease to be pretty soon but I love it.
5 lbs 7.4 oz

And this is with a BCM government barrel and 4.2 oz muzzle device (it's VERY front-heavy)

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V Seven parts:
Titanium Takedown Pins
Titanium Castle Nut / Endplate
Titanium 57-degree safety

(yes these are all wastes of $$$)

I still need to hack down the stock to fit the mini-milspec buffer tube better.

Lower: H&R M16A1 factory complete: 1lb, 13.75oz
Upper: Colt 6720* complete: 3lbs, 6.625oz

TOTAL: 5lbs, 4.375oz

Not a bad start for just slapping together an upper & lower I had laying around. (no sights/optics)

* Upper config...
-- Colt M4 upper receiver w/Colt FA BCG & CH
-- Colt 6720 16" pencil barrel w/A1 FH; ADCO shaved the FSB
-- MI 10.5" Ultralightweight rail

I'm wondering how much one of those KE Arms KP-15 lowers weigh (all in)? ETA: Website says 1.7lbs complete.
This lower here is SBR'd and I'll likely use it for something else.

Some  very nice LW builds lately. Glad to see these threads staying alive .