*** 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

Yeah, and subsonic 30-30 is tits out of an AR.

I didn't include the BCG and adjustable gas block for the AR308. The 2A titanium regulated bolt carrier group is only 11.55 ounces complete.

But there are two (2) problems with 2A Arms.

First they make an expensive $$$$ 6.85 pound AR 308, nice rifle but using a lot of the 2A parts isn't what 2 A wants. They really don't want competition (builders) beating them with their own parts.

Second they only make a 15 inch handguard at 10.5 ounces about 5 ounces too heavy. They are ignoring the need for an 11-12 inch 308 hand guard.

Third they only list an (31.5 oz.) .308 barrel, that's over 3 ounces more than the Faxon 16 inch barrel.

Four they use an 8 position buffer tube (4.3 oz.) and a T2 AR15 type carbine buffer. Using a V7 buffer tube and Taccom buffer cuts almost 3 ounces over the 2A parts.

OK that makes four problems.

But if you could use V7 parts or carbon fiber stock/handguard with the core 2A receiver set a 4.5 pound AR308 is possible

Not sure what your post alluded to. There are now 30-30 rifles with silencers.

But newer ammo like the LeverRevolution comes out of the barrel at 2400 feet per second, is very aerodynamic and will kill deer at longer ranges than the 300 BO.

About the only thing the 300 BO does well is silenced at under 50 yards. So it does have it's niche.

But there is no comparison of deer kills, the old 1895 30-30 has killed more deer than any two calibers in history.

Now the 30-30 has been built in AR's, but I would put the 7.62x39 Russian, the 6.8 SPC and the 6.5 G as better deer and hog platforms over both the 30-30 and the anemic 300 BO.

Another design goal of the 300blk was to use the standard AR mag. In fact use all the same parts but the barrel.

lest we not forget.

300 blk is a great "micro" action cartridge. When you need your gun to be small or subsonic but you still want some punch! The supersonic loadings are pretty good for how compact a gun you can shoot them out of. 147 gr from armscor is just under 2000 fps from a 8.5 in barrel. And it's not as brutally loud as 556 or 7.62x39 from barrels that short.

So we all agree the 300 BO is a niche round. Great for subsonic and very short range shots.

If we're being honest and open, there a LOT of truth posted above.  There are some at one end of the spectrum are getting a ton of free stuff, and a nice paycheck as well.  I've never had a problem being open about the details of the industry, and those in print and those with big youtube channels (before demonetization) have had opportunity to double dip big time.

While I'm sure someone's making money on my articles, I know it's not me!  I've made between $25-75 per article over the last 3.5 years.  Out of that comes gas, usually ammo, a couple hours of emails and phone calls to source a product, however many hours of actual usage and a couple hours to write it all up and edit the photos.  With a big article the time spent goes up a bit more, though I could be on arfcom less and up my productivity .  This is why you often see magazine features about some guy's rifle that's already built.  Minimize time spent, and get more cutting edge performance from an actual subject matter expert.

After all that is done, I usually have to send the product back.  I don't know if I do or not until the article is published, at which point my boss insits (rightly) that I offer to pay for it or send it back.  I got lucky on the Ultralight series though.  By the time I'm done with an article series (like the ultralight, or the ultrashort .300 blk barrel roundup, or the current "Acog Killers?" series), I'm so burned out on the subject I can't for a coherent thought for months.

In regards to the "unbiased" reviews, you're totally right.  I used to buy a lot of gun mags, and read a goodly number of sites.  Some clearly have no intention of writing a negative word, which does more to harm my impression of a potential purchase than the outright truth would.  I'm lucky in that my first editor at Loadoutroom (now elsewhere) and my current editor at Ammoland have insisted on honesty, and have never pushed me to hide a negative review.  I really doubt most writers are lucky enough to have that standard held for them, when they're facing constant temptation.  When I was hired at Loadoutroom, I was in a group of 10, all of us were Rangers or SEAL's.  Of the 10, 8 immediately got their first review item and never wrote a word.  That left two, myself and a SEAL, who proceeded to plagiarize an entire article, copy/paste.

I'm interested in revisiting the ultralight ver 3.0, and/or an ultralight AR10.  Truth is, unless I feature a gun from @Breastroker or someone similar, it just wont be in the top 10% lightest guns without a massive budget.  There's no way to get 100% of the industry leading companies to send/lend products for an article series.

I can (and have) improved on those ver 2.0 numbers passively over the last year, but to really make major gains (losses?) I'd need to start from scratch and replace both receivers.  The V7 2055 lower and bootleg 7075 upper aren't near the top any longer.  I could drop ~5 oz on those two alone.  Carbon fiber forend and stock, DSA sand cut bcg (with above mentioned RCA adjustable key) delete a couple unnecessary parts (port door, end plate), lighter pins, Ti grip screw, Oregon Rifleworks pencil barrel...

You may have talked me into revisiting it.  Who wants to trade parts?  

Ps, this is by far the longest post I've ever written.  I appreciate the engagement!  Now back to the ultralight goodies

I love .300 blk.  Is it the ultimate cartridge?  Hell no.  But what it does, is exactly what I want a round to do.

1.  Short barrel optimized (I'm 5'5", if I'm carrying a 16" barrel and bend my knees slightly, it's in the mud.)

2.  Suppressor optimized.  My hearing is shit, severe tinnitus as well and I'm still in my 30's.  Unless there's no other choice, I shoot suppressed.  The length of the can exacerbates item #1

3.  Longer range not needed (usually).  Most of my hunting areas are sub-100 yards, with 200 yards being max.  I dropped a mule deer last year just shy of 200, if it was a couple steps further I'd have been out of my personal skill range

Yes it's totally a niche round.  I happen to live in that niche.  All things being equal, if I still lived in Alaska I'd be carrying something bigger.  Spent most of my youth carrying an ought six, or .300 win mag when on Admiralty island (grizzly home base).  Oregon critters die easy.

Last few generations of my family slew countless deer and black bear with 30-30's, 25-35's and a .243.

But just for fun, I'll toss this in the pot:  My brother killed a bull moose with his .300 blk @ ~ 100 yards, using Rem UMC rounds.  He was clearly not prepared for the situation and I DO NOT recommend anyone try to replicate his kill.  Just because it worked once doesn't mean much, but it was a fun hunt and the meat lasted 4 households for a year.

Not really. Supers in 300 BLK are effective on human sized targets at ranges in which the vast majority gunfights happen, both civilian and military. It's not a sniper round, but then again sniping is a tiny (and frankly marginal in relevance) aspect of warfare and pretty much irrelevant on the civilian side outside of a revolution.

Agree it's a niche round I'd rather not have to deal with, but it is what it is. It's an important role to fill in my line up.

Rex, Thank you very much for your service and for your honesty.

But DAM, you got to be the smallest Ranger ever, or close. So you had to be BAD ASS.

Sounds like a AR308 with shorter barrel (14.5?) would be perfect for you. I found a CMMG with mid gas @12.5" length and a BA 12.5 inch barrel with carbine gas length. Supposedly about 30 ounces but companies lie a lot, except for Faxon. Of course for short Rangers they also make a 16 inch 6.5 Creedmoor barrel at 1.89 pounds so about 30 ounces.

I have talked to a lot of Rangers at the gun range, most seem to be 6 foot or slightly taller. One Ranger sniper spent a bunch of time helping my 10 year old grandson with the basics, kids were WIDE OPEN as this guy was still in uniform. He said they had a lot of fun shooting at filled cans of helicopter go juice at long distance, supposedly blow up great. Two months later he was out, had a full beard and drove the luxury Hyundai.

Also know a bunch of Seals. Several were 6'2 or taller, one was Chinese American maybe 5'8" but bad ass iron hand Kung Fu. As in he beat everybody in a tournament when we pulled into Kaoshung back in 1972. Youngest one was about 30 and only 5'7", but he told me a 140 pound ruck was nothing. He said many time he carried his own weight (160-165).

The one thing the Rangers and Seals had in common was intelligence, as in the top 1% of the top 1%. They wrote like college professors. I am told the Seals go to speed reading classes, as in a couple thousands of words per minute. Hey if they give you several 2000 page technical manuals on atomic bombs to read over night. LOL

Yeh many of us would love to see an under 5 pound AR308 from one companies parts or a 4.5 pound AR308 using parts from several companies.

I wouldn't hold out for the Oregon Rifleworks barrels being the lightest AR15 barrels.

Got a bit of an odd request. I'm looking for the lightest 15in rail possible that will clear an adjustable Adam's Arms piston kit. Would prefer a Keymod or Mlok rail.

You're quite welcome.

Funny story...  For a while I was the tallest non-NCO in the squad (about 6 riflemen, grenadiers and SAW gunners).

hence my nickname, the King of the Midgets.  In latin, Rex Nanorum (rough translation)

One team leader a bit later was ~4"11.  Laotian dude, tougher than.... thinking of a witty anecdote before coffee.

I'd love to see a 5 lb AR308 from the factory... really no reason not to, except for the eligible companies not seeing the potential market.

I'd like to see the bootleg RBC in Ti while we're at it.

And V7 team with Smoke Composites

Some companies make GREAT lightweight parts and then don't use them in their assembled rifles. I wrote to 2A Arms, their 6.85 pound XLR-20 AR10 6.5 Creedmoor is an example. To me it's way too heavy.

" While lightweight is one area of focus on our
products , it is always secondary to a few other attributes. Fit, function,
reliability, cosmetics and manufacturability all play a much bigger role than
just trying to make a rifle or component lighter. We can probably make a 2 lb
rifle, but it would look like crap. Haha.

I appreciate your passion for pushing the lightweight limits and supporting 2A
Armament. "

He left out profit as their primary focus. Rifle is still $2724. Also is he saying that their titanium parts are LESS reliable? Are their fit and function somehow less?

By simply replacing their full mass BCG with their titanium regulated bolt carrier group they would save over 7 ounces, add a Hogue 15 degree grip and they would be at 6 pounds. I used many of their parts like the Xanthos receiver set and the 2A barrel @ 20 inches, added some CF handguard and a Smoke stock and the 6.5 Creedmoor came in at 4.9 pounds. They use an 8 position carbine buffer tube so they can then use a cheaper AR15 buffer. By using a 6 position buffer tube and a 308 carbine short buffer they could cut another 3 ounces.

Heck they don't even sell their 8620 steel carrier (what they include in their rifle) separate anymore, why not add $100 to the price and include their 11.55 ounce titanium regulated BCG?????

The whole problem with ALL large frame AR308's is the BCG starts out too heavy, with AR15 carbine buffer they weigh over 23 ounces. That's why it slams like a sledge hammer. My 11.18 ounce titanium BCG and my under 1 ounce shorty 308 buffer comes in almost half the weight, and slams like a ball peen hammer.

I am sure they know the lighter you go the cost gets greater, getting a 5 pound bolt gun in a powerful cartridge usually costs greater than $4000.

So if they teamed with Smoke (already teamed with Faxon) they could sell their under 6 pound AR 308 and AR 6.5 Creedmoor for just over $3000. Guys who want the BEST and those who hunt in the Rockies or Alaska where hunts start at 5000 feet and go up to 10,000 feet would find a $3,000 AR 6.5 a game changer.

Surely if you're striking for a lightweight .308 class AR you'd start w/ a POF?

2A has certainly been a big supporter of the ultralight community. Maybe they don't sell complete rifles built the way we'd like them, but they are willing to make very niche items for us to use and that's pretty awesome. I seriously doubt that they sell very high volume on some of these things. Their Ti BCG is super niche, just based on price alone. It's never going to be a huge seller, but they did it. I'm not saying they did it purely for "the love of the ultralight game", they are a business and making money is their business, but let's face it, it's super niche and they were willing to push the boundaries and make it anyway. I think that's pretty cool. It's not the absolute lightest carrier, but it might be the most durable LW carrier and I'm guessing what they were trying to accomplish was not absolute lightest, it was light as possible while still being 95% as durable as a high end steel carrier.

I wasn't saying anything bad about their regulated titanium 308 BCG. They probably would be the lightest if they used a titanium firing pin and key screws.

What I didn't like is they are assembling their "lightweight" AR10's (Note that is an Armalite term only) using a 8620 full mass carrier that they don't even sell on their web site.

They make the full mass carrier seam like it's a good thing when it is absolutely the worst thing in an AR308. Full mass means using a heavy STRONG spring, an a jackhammer like action.

They make a 8620 steel regulated AR10 BCG that uses •Regulating gate: machined from 6AL-4V Titanium and for $399 is the lightest steel BCG @ 16.55 ounces.
Their titanium BCG weighs 11.55 ounces for $489. Maybe a little high $$ but worth it to have an adjustable gas system. Subtract the cost of a titanium adjustable gas block about $100 or more, their regulated Ti BCG is a steal!

When I got the first Toolcraft titanium 308 BCG their price was close to $489.

I actually don't think the ultra lite weight AR308/6.5 Creedmoor parts are a niche market anymore. At various times of the year many 308 AR parts are completely sold out. The large frame AR308 is now the new Barbie for men.

The 2A titanium regulated 308 BCG is sold out at this time. For three years they wouldn't sell a separate Xanthos 308 upper without first having to buy the set.

Now you can buy the upper for $309, add a military or LEO discount and that is a PERFECT start to an ultra lite large frame. Add a Faxon lightweight barrel and a Tennessee Arms $60 polymer lower and anyone is on their way to an under 6 pound AR308. Go crazy with all the other lightweight parts and you can be under 5 pounds.

Yeh I agree 2A makes GREAT parts, quality parts that happen to be lite weight.

For those who want to build an ultra lite weight AR308, right now Primary Arms has the Faxon 16" pencil 308 bbl of 28.4 ounces for only $196.80

Add a Ghost upper receiver @ $75 and you have the start for an ultra lite AR308. The Ghost at 11.7 ounces it is one of the lightest normal priced large frame uppers. It is DPMS pattern low rail, and has no FA. I have often stated there is no need for a FA in a 308. I could get a 2A Xanthos upper that weighs 9.0 ounces but it would be over $310.

For reference the DPMS uppers weigh 16 ounces and 17 ounces each.

Add a Smoke CF handguard and no bother about rail height. Add a Smoke stock or a 3 ounce 6 position buffer tube and a minimalist or Rogers Super stock.

Next to the 2A Xanthos lower, the DPMS 308 lower is the next lightest available. Of course you can get the 80% Ghost lower receiver and cut the heck out of it.

Or add a Tennessee Arms lower in polymer $57.99 and you got the start on a 5 pound AR308. Of course you can get the PURPLE version for only $43.99. If you like camo they do that for $25

Right now is the start of great buys for your next light weight. Heck the Faxon 16" 556 pencil barrel is only $133 at Primary.

Only if your bias keeps you from doing an accurate comparison.  Hornady's numbers are from a 24 inch barrel, most of the numbers for supersonic 300 are from 16 inch or shorter barrels.  Corrected for barrel length, performance would not be significantly different.  They are both 30 caliber bullets, going nearly the same speed (from the same length barrel).  Do you really think the 30-30 is a magic deer killer?

It's also really good at not being fired out of a lever action rifle, really good at having a subsonic option, really good at not loosing performance in shorter barrels, and really good at working in guns that hold more than seven rounds.

Which is good at supporting an emotional bias, but has nothing to do with the performance of modern bullets at hunting ranges.

There is no arguing with some one who loves their favorite rounds. Almost as bad as the 6.5 Gremlin people.

This thread is about light weight parts. Not about favorite rounds.

What you got on light weight parts?

I see that the In range TV guys and Brownells have teamed up to start making WWSD2020 rifles. I'm glad that there's interest in lightweight AR stuff, but I wonder if they will be going to the source this time. I don't mean the PWD necessarily, but this thread and the people that contribute to it represent the absolute bleeding edge of AR15 lightweight tech / knowledge. The lightest rifles in the world are here. The means of 'democratizing' that knowledge with everyone is here. Will they tap that resource or compromise the stated mission due to a need to only use parts/vendors that work with Brownells? I dunno, time will tell. All I know, is that if they really want to go light, this place is THE resource.

Given that Brownells is undertaking to sell their rifle designs, it would seem that Brownells would reach out to vendors whose parts they don't currently carry.  The WWSD project didn't seem focused to me on lightweight @ all costs - it seemed to focus on using some of the best improvements available to the AR that were in touch w/ the original design philosophy of using the latest materials technology.

The captured JP spring/buffer, for instance, seems to be more about soldier proofing the rifle and eliminating parts count (buffer retaining detent, detent spring, detent roll pin) than pure mass.  Are Gun Jesus and Gun Satan following this thread?  I bet they look @ it from time to time.  Are they pursuing the absolute lightest receiver in the WWSD 2020 project & Cav Arms redux through the KE Arms Mk 3?  No, they're not.  They're pursing a lightweight receiver that has flexibility characteristics that metal receivers do not.

I know they aren't going light as possible, i guess what I'm saying is 'i hope they don't chose part X because it's "Brownells compatible" instead of the lighter / better part Y that isn't".

I just got a Black Friday email from Faxon. Some of their expensive barrels are 50% off and most will be 20% off.

But they have a AR15 rifle at 4.95 pounds. One of the lightest AR15s available., and one of very few using an adjustable gas block. Using a BCG @ 8.5 ounces.

So lightweight is really going main stream.

Faxon's Ion Ultralight Rifle (FX5500):
•14.5" 556 Pencil Barrel w/ Welded 3-Port Brake - Meets NFA 16" minimum barrel length requirement
•Enhanced Forged Receiver Set w/ Tensioning Screw
•Gunner Lightweight BCG w/ Superfinish
•13" M-LOK Carbon Fiber Handguard
•Multi Position Adjustable Gas Block
•Hiperfire EDTDM Single Stage Trigger
•Radian Raptor LT Ambi Charging
•Radian Talon Ambi 45/90 Degree Safety Selector
•MFT Minimalist Stock
•Magpul MOE® Grip
•Mid Length Gas System

Probably most importantly, the KE Arms Mk3 is compatible with Magpul PMags. It also sports an enlarged trigger guard, flared magwell, and MLok slots on the top/rear of the stock.

And since the lowers are injection molded, they are inexpensive at only $99 for the entire stripped assembly

I have a cav arms mk 2, or, more accurately, my wife has one on an old school LW build.

I just can’t make the jump to polymer receivers. Not sure why really, I have several poly handguns.

I do see the AR industry moving in that direction though. At least for LW offerings I’m thinking we will see more and better poly sets hitting the market.

The KE Arms Mk 3 is presumably compatible w/ Gen 2 PMags, as opposed to the Sabre Defense & GWACS roll-marked Cav Arms Mk 2, in which the Gen 2 would feed fine but not trip the LRBHO.  Gen 3s are fine in the Mk 2, however.

The monolithic lower is a cool idea, but so long as it has a clone of a mil stock it'll never be all that light.

It also stikes me that the premise of the WWESD / Brownells project is a bit off target in that it is about how things would be done with the materials, methods, knowledge etc we have today.

The problem, they also have to keep their designs compatible with the AR eco system, which limits what changes they can really do.

If the knowledge, parts, materials, processes we had today were available and it were truly ground up - the lower may be polymer but it simply wouldn't compatible with spec AR upper, etc.

That said, cool project...

If you want to leave the AR platform & go polymer - you end up w/ the ACR/SCAR - both of which are heavier, b/c they're outside the AR platform aftermarket.  For all the limitations of the majority platform, the aftermarket generally makes it worthwhile.

Agree, ecosystem is what make it what it is these days.

Random blurt- the nylon grip screw is holding up fine. I have extras if anyone else wants to give them a shot, let me know.

You can get 1/4" nylon screws @ Home Depot or Lowes.

I will bite, how much does a nylon grip screw weigh and how much less than an aluminum or titanium one?

Nylon grip screws.

Sounds perfect for my build.

Although it is on an indefinite hold.  I'm planning on getting a new gwacs lower. So I may not need one.

Sorry for the delay, the nylon 1/2" long screws weigh .0282oz. each.

I find you fringe guys interesting with these ultra lightweight builds. I have a couple lightweight builds and just have a hard time with certain compromises that seem so easy for many of you guys to accept and it makes me wonder if some of my thoughts are too conservative.

My build concepts have been about sacrificing NOTHING, other than money, for parts that used lighter appropriate materials, but still allowed FULL functionality, reliability, accuracy, etc. vs standard weight counterparts.

Nylon grip screws, aluminum bolt catches,  weightless buffers, aluminum carriers, exposed/skeletonized parts, etc. just takes the system a bit too far into a functional/reliability window that I believe can be tempermental, limit accuracy, overall balance, and utility. At least those are my current thoughts.

Why do you guys think there were buffer weights in the original AR design instead of just using a polymer buffer... the original AR took an almost no holds barred approach to cut weight for its era, with pencil barrel, lightweight flash hider, lightweight car stock, etc. yet the lightest carrier was the 3oz carbine buffer... which is the lightest buffer I use. I am not being condescending... it's an actual question...  was it just for full auto cyclic rate control in your opinion?

I have never had a reliability issue but I am not as weight militant as many of you guys. My lightest carrier is a JP LMOS and I own 4 of them. Not the lightest, but heavy enough to run suppressed, made of steel for higher volume fire, etc.

My precision and 300 BLK builds use an H1 buffer because of suppressor use. My lightest build actually uses an LWRC ultra compact stock to allow a shorter LOP for a female or child, and the buffer is around H1 weight, and it balances the gun better IMO that my lighter stocked guns, though I wish it was a tiny bit lighter. Would I be better off swapping the tungsten weights in that 2 weight micro buffer for standard carbine weights on that build if it is never suppressed?

I run a BUIS on defensive carbines with red dots, even lightweight builds. I have not found a BUIS that is lighter than my MBUS poly that is as tough and functional... dont like the attachment method of Griffin Armament for example. I also dont run a Deltapoint Pro on those rifles (and I own 3 of them) but run T1/H1 on my lightweight builds, because the DPP is just too fragile for a defensive rifle. I dont have any range toys, per se, and I have shattered a DPP from a short waist high fall.

Anyne have any input on lighter BUIS, lighter carriers used with suppressors, or lighter buffers with suppressors? Is there a bolt catch that is lighter than my V7 that is strong enough to put on a duty rifle?

I've heard of more RMR failures than Delta Point Pro failures. The DPP has been heavily abused in pistol applications, which is much more abuse than an optic would see on a carbine, so I'm not sure what evidence the skepticism of their durability is based on.

As far as ultralights in general, some people just like to push the envelope to see what's possible. The comp crowd and the ultralight crowd drive a lot of innovation in the AR world. Personally, I don't even use an AR for SHTF (Tavor SAR here), so all my ARs, light, heavy, and otherwise are range toys. That said, ultralight principles can be applied to greatly reduced the weight of many kinds of builds. The AR is supposed to be a lightweight rifle...yet MANY builds you see online are 10+ pound pigs.

Keep in mind...

Many of the builds you see here are what I would consider novelty pursuit builds. I have at least one squarely in that category, but still don't have any plastic receivers yet. In any event, these are not rifles I would take to a course, grab in defense when others were available, etc... they are simply how light can I make this build but still meet these requirements. Its a corner of a hobby.

As far as the buffers - PursuitSS will be best to go into where he's found reliability and at what level there. You can go pretty light and if all else is tuned right the rifle goes with out issues. As far as how light and what compromises come I guess that's not all entirely clear to me. Why do you think an H1 is needed with other modern components?

For BUIS, with primary optics becoming so reliable, you can compromise more and more on BUIS as the chances of them being needed get less and less. That's how I see that.

I use 2A and now the DSA Sandcut on actual defense rifles with suppressors, so ya. No issues.

I consider there to be 2 classes of lightweight ar, your "ultralight" consisting of rifles that use components that aren't quite what you could use for severe duty or full auto. Examples would be my 3.2 lb 556, 4 lb 50 Beowulf pistol, and 4.4 lb 308. I'm using polymer receivers (upper and lower for the small frames) and as much polymer and magnesium/aluminum as possible everywhere else. This type of weapon I'll mainly use for hunting trips where weight savings is a primary concern or just to get "wows" out of people when they pick it up. I tried lightweight bcgs and buffers in multiple echo trigger builds and the more spring and buffer/bcg weight the better. The lighter stuff is fine for semi auto as long as the gas system is adjusted properly and you don't get it too fouled. The other class would be what I categorize as "duty" grade lightweight rifles. Full auto/echo trigger capable weapons where zero reliability is compromised. I have 4 that fit this category, and they all make extensive use of titanium and aluminum for small parts, fostech magnesium lowers with their bossed stress points, and chrome lined hbar or m4 profile barrels.

BTW, anyone looking for a Faxon 14.5" pencil for pin/weld LW rig might wanna check out the BF pricing at Armorally.com. New vendor to me, but $110 shipped is a nice price on that bbl. In stock too.

I think Nada said it well, pushing the extremes is fun for some and i doubt they are building 3lb rifles to defend their family with.

Buffers are designed to reduce bolt bounce in an attempt to eliminate the chance of light strikes during full auto fire. A buffer is not necessary at all for semi auto, the original design featured a plastic spring guide until they encountered issues with bolt bounce during higher rates of fire brought on by a powder change and a pressure increase. Heavier barrels increase carrier bounce and so heavier buffers were created. The reciprocating weights in a buffer are only needed to ensure reliable operation of select fire rifles. While the weight of the buffer does impact the cyclic rate that is not the intention.

The reason you see people running heavier buffers in this situation or that situation is in an attempt to delay bolt unlock. Its a sideways attempt at fixing the symptoms of too much gas. Adding a suppressor increases gas port pressure as well as the amount of time that port is pressurized. This starts the carrier moving backwards and the bolt unlocking sooner than we would like it too. The easiest fix is to add mass to the action, thats why you see people running heavier buffers here and there, its a quick fix for excessive gas. The additional weight is not necessary for any reason other than to slow down the extraction process. Delaying the extraction process can be accomplished through several other methods the best method being an adjustable gas block, metering gas source. An alternative is limiting the amount of gas that makes it into the piston chamber in the bolt carrier. Adjustable gas keys or bolt carriers can be a great drop in solution. Increasing the action spring rate can also help alleviate symptoms of early extraction. Reducing action weight of a suppressed rifle would not be recommended unless the gas system is adjusted to accommodate that reduction.

My suppressed 5.56 utilizes a bootleg adjustable carrier with a 1oz stripped buffer and a strike industries flat coil spring. This is a rifle that i depend on. Total weight with suppressor is 5lbs 15.5oz

Nice build Jered!

Devl, hang around here awhile and you will get the mindset with these ULW builds.

This is a great group, and it’s really interesting seeing the ideas and innovations the come up

2A has a 20% off sale going. Picked up the adjustable Ti carrier from them for 320.00

Happy Thanksgiving to 2A Arms. That would put the Xanthos upper $60 less, very close to others heavy upper receivers.

Speaking of black Friday deals. I picked up that day arms bcg for 120 instead of the typical 160.

My build may actually be finished this year.

https://www.dsarms.com/p-17128.aspx?searchEngineName=dsa-ar15-enhanced-low-mass-aluminum-sand-cut-complete-bolt-carrier-group-556-223-300-blk

Have we talked about the KaiserUS polymer upper & lower w/ aluminum inserts in the last 100 pages?

I just got my AR built up on an OD green set of the X-7s, I really like them.

I'll probably post up my build once I swap out my current Phase 5 LPSN handguard for a Coda Handguard I ordered.

My lightweight Beowulf pistol uses a Kaiser receiver set. No problems, just follow the assembly instructions. Only use a reaction rod or Bev block. Don't buy Kaiser's cheap aluminum knockoff reaction rod though. Ask me why 🤣😂