*** LAST UPDATE 4/14/2024 ***
This is intended to help people who want to build lightweight rifles and/or want to lighten up an existing rifle. This is not necessarily intended to be a comprehensive list, as it only includes parts that are lightweight or nearly so.

RAW DATA SPREADSHEET HERE, v1.03

An updated Parts Database made by another user is here:  
Check this Google Doc
It may be more complete / more updated.

My recommended cheap / light build if you only want to get under 5 lbs for ~ $1k.


For a little more money (about $150 more) you can save a few more ounces


Key:
U = User Data
M = Manufacturer
C = Calculated

Weights listed are in ounces.

Parts in purple are amongst the lightest options


****Upper Parts****
Muzzle Devices
A2 Flash Hider       2.15 U
A2 Extended
Mag Tactical             1.90 M
BE Meyers               2.50 M
AAC Brakeout 51t   4.20 M
AAC Blackout 51t   4.30 M
VDI Manimal            1.48 M
Rainier Mini-Comp    1.44 U
ALG Single Chamber Brake 2.01 U
V7 Titanium   1.35 M
V7 Ti V-grooved  1.25 M
Venom Defense hybrid steel muzzle brake 1.48 U

Charging Handles
PSA Milspec  1.13 U
Breek Arms Warhammer 1.0 U
Spikes Milspec 1.07 U
Rainier Raptor 1.42 U
BCM Gunfighter Med   1.24 U
BCM Gunfighter Small
V7 Ultra-light charging handle  1.04 M

Bolt Carrier Groups
LMT Semi-Auto 11.14 U
Umbrella Corp Full-Auto 11.46 U
RRA Semi-Auto 11.26 U
Spikes NIB FA 11.8 U
Colt F/A BCG 11.56 U
BCM F/A BCG 11.64 U
PSA F/A BCG 11.50 U
Red X Arms Ti 7.81 M
JP LMOS Bolt Carrier 6.25 M
JP Bolt Carrier (full mass) 8.5 M
Young Man. SLC carrier   7.1 U
FN Bolt Only 1.5 U
Smith Aluminum carrier w/ key 3.7 U
PM&T Ti carrier w/ key 5.1 U
V7 Systems Ti Carrier  5.7 M
V7 Systems Ti BCG  7.9 M
DSA Low-Mass Steel BCG 9.1 M
DSA Aluminum BCG 5.2 M
OdinWorks Low Mass BCG (steel) 9.0 MU
WDR Titanium BCG  7.8 M
FosTecH LOW MASS BCG (Nickel Boron) 8.5 M

Gas Blocks
Aero precision 0.625 adjustable
BCM 0.75"  1.30 U
BCM 0.625" 1.928 U
Daniel Def LPGB 0.750        1.28 M
Daniel Def LPGB 0.625        1.92 M
V7 Systems Ti LPGB 0.750  0.74 M
V7 Systems Ti LPGB 0.625  0.71 M
2A Armament Ti 0.750   0.70 M
VLTOR 0.625" (set screw)  1.4 M
Parallax Tactical LPGB          1.47 U
SA 0.75" adjustable 1.8 U
Samson MFG lite 0.625"  0.6 U
YHM LP w/ set screws 1.43 U

Gas Tubes
Del-ton Carbine 0.63 U
Carbine Length  0.7 C
BCM Midlength 0.757 U
V7 Midlength 0.94 U
Mid Length  0.8 U
Rifle Length 0.9 U

Dust Covers
Dust Cover Assembly  0.75 U
Dust Cover Ass., V7   0.37 M
Mako Poly Dust Cover: 0.2 (discontinued?)
UBCM Dust Cover 0.506 U
BCM Dust Cover Pin 0.211 U
BCM Dust Cover Spring 0.021 U
Strike Industries Ultimate Polymer  0.3 M
Strike Industries Ultimate overmolded Polymer 0.5 M
Strike Industries Polyflex  0.3 M
Magpul Polymer   ?

Forward Assists
BCM Forward Assist 0.712 U
BCM FA Spring 0.058 U
WOA Forward Assist Assy  0.74 U
Northtech Ti Forward Assist 0.501 U
Northtech Ti FA Spring 0.050 U
Schuster Mfg FA plug  0.10 U

Upper Receivers
2A Armament Balios Lite stripped, no FA  5.8 M
Aero Precision Forged Stripped 7.16 U
Aero Precision Forged Stripped; no FA   6.4 U
Fostec FLITE Elite Stripped 5.92 M
Kaiser X-7 Poly Upper: 5.5 M
Mega Arms forged stripped 6.9 M
Mega Arms Billet Upper, 9.4 M
Rainier Forged, Complete  8.6 M
Rainier Arms Forged Stripped 7.08 U
Spikes Forged complete: 8.4 U
V7 Weapon Systems Forged Complete 7.7 M
V7 Weapon Systems Forged stripped 6.8 M
V7 Weapon Systems Enlightened 6.0 M
V7 Weapon Systems Enlightened (lithium/aluminum) 5.8 M
Forged no FA, complete  7.3 C

You bought the tool? It was included with my set that I got from Robar's closing sale, didn't get a ejection port cover though.

Yeah I had to buy it. This was years ago, lol I also didn't get the ejection port cover. The aluminum reaction rod broke, lol. In case you didn't figure that out yet 🤣😂 There are good German knockoff reaction rods in small and large frame, they're not expensive and they're made of steel. The Bev block is my favorite assembly tool though, it's idiot proof. I really like the Kaiser set though, not the lightest but the "match grade upper and lower fit" really is very good, lol. And it has high strength anti rotation aluminum inserts molded in at all the right places, including the gas tube hole. If the buffer tube neck had some kind of reinforcement I'd use them on my "duty" grade builds.

Use a thumbhole stock.

My AR isn't the rifle I'm likely to pick up if I need a gun at that moment, so I'm not too worried about the durability. Doubt I'll be able to break the lower unless I'm trying to do it anyways.

This is more of a fun/back up lightweight rifle in case my AUG goes down. Using lightweight components for all the larger parts, but keeping full weight components for the small parts that I don't lose much weight for the extra cost. Finally got rid of that stripped screw now, so I can throw the damn 1lb+ handguard into the parts bin.

Does anyone have the weight of the Sig Romeo 5 without the mount?

All of the weights listed have it with the mount at 5.1 ounces. I'm thinking of putting it on the scalarworks T1 mount until my Micro T2 arrives.

Mostly done. I'm still waiting on the Micro T2 which should only add another 3 ounces. As it sits(without magazine)its 3lbs 13 3/4 ounces. I'll be 3/4oz over my 4lb target if the Micro is true to it's advertised weight.













Honestly, I didn't realize how light an AR could be until I built this and it's not even in the neighborhood of the super light ones here. My next lightest AR is just a hair under 6lbs and this thing feels night and day in comparison. Now...hopefully is shoots!

Is that the builders series receiver? What barrel? We can see most of the parts, Hogue grip, Minimalist stock etc.

It sure looks nice.

Man I was glad I stopped in and seen your post the other day!  I was able to pick one up for $120 also!   Thanks for taking the time to post this deal!

I don't suppose you've taken the risk, and tried doing push-ups off a gun with the Kaiser receivers? 😜 If I can see a gun take that treatment without the receiver extension snapping off I consider it strong enough for duty purposes. The problem of course is finding someone willing to spend perfectly good money on gun parts, then record himself trying to break them.

It's cool InRange was willing to do pushups on CavArms lower, but damn, I wouldn't have done that to any of my guns.

Damn nice LW gun. I like these kinds of builds where it has that “normal” look to it, yet only four pounds. An adjustable stock and high quality RD even!
What is the barrel length?

There is a shortage of LW mounts. I used a $20 Scalarworks knockoff Mount for my RMR that I found on Amazon.  I further milled it to a final weight of .896 oz.
It’s made with a softer 6063 aluminum but it seems plenty strong for an AR.

Nice work Loonytic

I used the 10.5 inch Faxon lightweight barrel in the 2A Palouse set. I'll post my build list soon...just gotta format the spreadsheet.

Nah man! I've done pushups on mag tactical and fostech magnesium receivers though. They passed! 😁 The Kaiser has an aluminum threaded insert for the buffer tube but the neck is still just polymer. It'll snap if you abuse it enough. And I know even forged 7075 can crack if you beat on it enough. I've seen a Colt m16a2 lower crack at the neck after only 30 years (lol insert sarcasm here) of combat and training!!! I just don't trust the polymer neck for any life or death gun.

Really nice blend of 2A and V7. Good shit man, looks like a solid shooter. Im curious to see the rest of your build list. Shaving 3/4oz off that stock shouldn't be to difficult. If you don't mind the look, a standard Car stock from brownels could save you enough OZ to run a nice charging handle.

That's an idea cause lemme tell ya...that Luth-AR charging hands SUCKS! I get the whole retro thing but it is very uncomfortable to use and just doesn't work that great in general.

If anyone is wondering...the Romeo4 weighs 3.0oz without the mount. I assume the 5 will be the same. I dropped the Romeo4 on the rifle today and like I thought, 4lbs 3/4oz.

You're welcome I just got mine and man is it light compared to standard.

I weighed my build and it's just missing the poly lpk from new frontier. Everything else is present.

I changed the buffer assembly from standard. To my armaspec because it weighs 6.6oz. So it should account for missing parts and standard buffer.

Attached File


So I'm going to count this as the official weight

I hope this isn't considered cheating by saying I'm done when I'm not. But even when I get the lpk. I'm likely not going to install it.

I'm really wanting to put this on the new wwsd poly lowers when they come out.

What the whole thing looks like.

Attached File

How's the See-All? Thinking of swapping my current UH-1 for one cause I've yet to find a lighter red dot that works with my astigmatism like Holo sights do.

That see all is my official optic whore. It always finds itself on new builds. As far as an optic it works well as a battery-less red dot type thing. The newer ones have tritium too for night.

I would suggest the newer one with the side thumb screw over this model. As the screws F up every thing you mount it on.

I believe it's found its home on this upper.

https://seeallopensight.com/

Oh snap and it's on sale too.

That's good to hear, and the sale is certainly tempting. The crosshair reticle for the Mk.2 seems weirdly busy, which sucks cause I'd prefer it over the delta.

Its done when you say its done!  Its lookn good, I like it.   I have a few of the same handgaurds, They are great for a lightweight build and look good!  I dont recommend the 16 or 17 inch long rail tho, it bends way to easy and way to much! Lol!  Unless thats not a problem on a certain build like mine!
 Keep us updated

I agree, nice build bacon!

Anybody have any pointers on getting out the barrel nut and trunnion out of a Coda Evolution handguard? I just got mine and I pulled the screws and the trunnion refuses to pop out.

Screw it onto a receiver, pull?

Gave that a go, but no luck. Threw it in the freezer to see if that'll help.

Got the handguard pulled and installed. Weighs 5 pounds 3 ounces with the Huey on there and unloaded.

It's a 14.5 Faxon Gunner P&W built on the Kaiser X-7 polymer receiver set. Brigand Arms stock and a 13.5" Coda Evolution handguard. Also using a Taccom buffer and spring with a low mass RTB carrier. Nothing else in the build is for lightweight purposes, so it's not nearly as light as it could be. Love how light it already is though.

Looks great writerclark.

I’d never heard of the Coda handguard before. I don’t see It in the PWD even but I checked out their site.
It looks badass.

Yeah, didn't hear about 'em till a month ago, and I really liked the mounting setup for it. Mine had a bit of extra resin around the trunnion area, so I had to freeze it for half an hour, screw it onto the receiver threads, and practically mortar it to finally free the handguard from the trunnion.
I think my only complaint is they only have 4 lengths. Would've preferred an 11", but it was either 13.5 or 9" and that'd show too much barrel.

Now I just need to decide if I'll keep the Huey on it, or find something a bit lighter to get it under 5lbs.

It's weird to have an AR that's the same weight as my little brother's 10/22 without the Huey on it.

I ordered a 9" Coda handguard on Black Friday too. Also ordered a 12.3" BA Hanson for it. They'll mate to a Frontier Arms side charger upper and WWSD lower when that becomes available. Will eventually be suppressed. My first SBR and suppressed rifle!

Where on the polymer Mk3 lower are you going to engrave it?

That's a solid question, would probably have to figure that out for the Kaiser receivers too

I guess I assumed they had serial numbers on them already? This is new to me so what am I missing?

When you build an sbr (short barrel rifle, any firearm 50 Cal or under with a barrel under 16" and a buttstock) you have to engrave your information on the Firearm and do a tax stamp. I like pistol braces, lol they're easier.

Should be plenty of space on the new WWSD lower to add this info, no?

Plenty - you have both sides of the stock.

Thought about it, but all the carrier/buffer systems I'm interested in are carbine length only.

I like the SB tactical sba3 and sba4 braces. They go on a mil spec 6 position buffer tube. So you would still be using a carbine length buffer. The sba3 is pretty lightweight, I'm using it with a v7 2055 buffer tube on my lightweight Kaiser polymer 50 Beowulf but if you were feeling spendier you could use a carbon fiber tube too. I really like the wwsd lower but I hate paying $200 to the government for something that should be 100% legal. Oh and not to mention waiting 6 months until they tell me whether I can have it or not!

Also I feel I need to point this out, stamping a polymer lower could end up being a costly and time consuming mistake.

I like that SBPDW. Wonder if it is kinda heavy for a lightweight build?

My scale isn't exact but, it is almost always exactly as shown on the PWD. Build list:

 

Being that close to going under 4 pounds would drive me crazy, OK crazier LOL

Pretty easy to get under 4 pounds, using a Taccom buffer and spring or buffer without weights and a 300 BO Spring. About 2.5 ounces less.

How do the Glock SBR folks engrave their lowers?

For pistol braces, I don't think it's worth it. It's not any more compact collapsed than an SBA3 is (in fact it's exactly the same), but it's far more expensive and several ounces heavier. PDW-style stocks are a nice option, PDW pistol braces not so much.

Speaking of braces, does anyone know of any good options for a 1913 receiver mount (i.e. the Sig MCX style moun) other than the Sig PCB brace? I've been eyeballing this bolt carrier, and am looking for other options for the ass end of the rifle.

Your not kidding! I posted my build on the picture thread. I was shooting for 3 pounds and ended up at 3lb and .29 oz.

My plan is to SBR it anyway so when finished it will be just under 3 lbs with not one single polymer part.
I’ll either use a thread protector or an aluminum muzzle device of some sorts to get where I need to be weight wise.

I made this aluminum flash hider playing around. It’s a little crude, I’m no machinist!


It’s under 1/2 oz. at .441 oz, but I have no idea if it will hold up at all. I don’t have a gun to even try it on right now. It may last a few rounds or who knows, maybe a few thousand?? Most of what I have read says it will be gone in short order.

Does anyone have the gun, range time and ammo to run it to its death? I’ll ship it to you to try out as an experiment.

I drilled a hole in it to use a pin wrench to tighten it up but in my ultimate wisdom I put it in the wrong location....🤬.

Not an issue since it’s just an experiment anyway.

I'm not sweating it too much. It's a solid rifle with an adjustable stock(something that was important from the start). Some of the parts came in higher than their advertised weights by a little and I knew I would be over 4lbs. Removing all the buffer weights should get me there and I plan on testing it this weekend at the range. Will report back.

The sbpdw is very heavy. The sba3 is the lightest option. The gear head works tailhook mod 2 is pretty lightweight too but you have to use their proprietary 5 position buffer tube.

For compactness check out the maxim pdw brace. There's nothing more compact and it still gives you a decent length of pull and 4 positions! It uses a short proprietary buffer and what appears to be a cut down 308 strength spring but you have every buffer weight option available from 3 oz to h3. You could always take the reciprocating weights out though 😁 Pricey but I love mine. Oh and to answer your 1913 brace question I like the palmetto State armory triangle folding "brace".

https://palmettostatearmory.com/psa-ak-p-ak-v-triangle-side-folding-brace.html

You're welcome ;) That bufferless system looks fantastic btw!!!

Thanks! Don't suppose you have the weight of the AK-V brace? The Sig PCB comes in at around 10-11 oz. That Maxim PDW is nice, about an inch and a half more compact than the SBA3, but unfortunately still heavier than SBA3+CF Buffer tube+buffer system, even if you use the chunky JP SCS buffer.

I don't have the weight sorry, I've just been eyeballing it! I do know the folding latch is steel and the brace itself is polymer though. Yeah that maxim definitely isn't lightweight but when you want compactness, which is what I went for in my 300 blk build, it's the best. I originally had a 6.5 in v7 barrel but I learned that direct impingement for a barrel that short is a bad idea!!! I was constantly cleaning unburnt powder out of the action and not to mention it stung my face with every shot!!! I switched to a 8.5" CHF double chrome lined fn barrel and all has been well.

We've got some guns to test and a friend has a registered M-16 lower so I'm happy to screw in on a 10.5" machine gun, 12.5" upper, 14.5'" upper, I think my buddy has a 7.5" upper, too.  SBR and M-16 would give you a durability idea pretty fast.

Shoot me an email if that's something you'd like to have me try.  Happy to send it back for you to analyze, too.

stitchclimber1 at gmail.com

It's stitch!!! The man, the myth, the legend!!! 😁 Larry cook us up some more of those aluminum 3 prong flash hiders!!! They look sweet! I'll take 1 in each caliber. As far as durability I've only seen 3 ultralite aluminum muzzle devices. Mag tactical made a 7075 aluminum muzzle brake that was pretty effective. I used it for a while, it held up pretty well but it wasn't that light. There wasn't an expected round count stated by the manufacturer. Probably cuz mag tactical sucked!!! The anarchy outdoors a-hole micro is 6061 aluminum and it has an expected round count of "well beyond 4000+ rounds". They said they tested with full auto too. I liked mine. Last up is the discontinued dark hour defense 7075 a2. This is by far the lightest. Dark hour stated on their site that they would last over 1000 rds. Seems kind of conservative since mine has lasted longer than that but I'm sure they pulled it from the shelves for a good reason. I'm pretty nice to my ultralite builds though, they never get too hot.