Newbie here so hopefully it's not too crazy...but I'm looking to build a lightweight (less than 7lb) SPR (no more than 18 inches, sub-moa) for $2k or less before optics.  Would love to hear some suggestions.  Right now Im thinking the Balios lite upper/lower, BCM KMR handguard, JP ultra LMOS BCG+Bolt, White Oak 18'' barrel (could use a different barrel if it's more accurate and still shed weight) and ACS stock.  What would y'all add / change?

So. Light weight and accurate don't play well together IMHO. Uber light barrels, don't tend to hold accuracy well. I'd stay with woa barrel. They are a known company for making accurate tubes. It's gonna be hard on beleive to go sub 7 pounds I'd beleive.

Agreed but i feel that the parts I selected should limit the weight somewhat. Do you see any parts in their that'd be incompatible with each other? I know JP's furniture require some special modification no?

Maybe a lighter barrel like a 16" Hanson from Ballistic Advantage. I have a 18" from White Oak and it's a shooter but it's not light. I really want to use a Hanson on a recce but I want to be able to use my AEM5 so I'll have to go with a Government profile instead. But I am really tempted by the Hanson with a sandman s or an omega.

Nice! I've got an omega in stamp swamp right now. Always thought of BA as a minor leagues barrel, does it actually perform on par with WOA or JP?

The Larue PredatAR is a good middleweight barrel option.  Still pretty solid under the handguards, but it gradually tapers towards the muzzle.  It's about the same weight as an M4 barrel (18" is 29oz or so If I remember correctly), but the weight is better distributed.

Maybe. Haven't read any reviews on the Hansen barrels. With a light profile you are potentially making yourself more open to stringing during high round counts. And remember. Hanging a heavy can on a light profile barrel, may subject you to some extreme poi shifts between suppressed and un suppressed.

A 16" Faxon gunner profile barrel would be worth looking into.

I think white oak is still the choice given the accuracy, but can shave weight elsewhere. Is there a bcg that's lightweight that doesnt cost 400$ like the jp?

With that kind of budget, your goal is no problem.  The following build comes in under 6lbs stripped and should be around 1/2moa if you can shoot that well:

**Upper**

- Barrel:  Melonited Lothar Walther 16in socom profile: www.customar15.net/shop/ar-15-upper-receivers/barrels-ar-15-upper-receivers/lothar-walther-16in-223-wylde-match-grade-barrel-stainless-melonite/  +matched bolt $345.

- Upper: Aero no Forward Assist $80.

- Handguard: Brigand Arms ATLAS $349

- Gas tube: Cheapest melonited ~$15.

- Bolt Carrier Group:  TS Arms Lighting Carrier+cam pin $230 + coated firing pin $8 + cotter pin $4.

- Gas Block: Superlative Arms .750 Clamp On AGB $100.

- Charging Handle: BCM or Griffin Armament is great for ambi, if not DPMS $10.

- Dust Cover: Strike Industries $15.

- Muzzle Device: A Suppressor. You can get this down the line, and use either a mounting device (for w/e suppressor you decide on) or cheap A2 ($5) in the meantime. Surefire, Amtac, Rugged, Delta P Designs, Allen Engineering, Silencerco, SIG, and KAC are pretty much the best right now.  

- Irons: Magpul BUIS $65.


**Lower**

- Lower Receiver: TNARMSCO reinforced lower $40 (if you aren't comfortable with poly go with a V7 Lithium or 2a Armament Balios).

- Small Parts: Standard LPK without trigger. Can also buy individual lower parts from White Oaks Armory very cheaply ~$35 or less.

- Trigger: Hiperfire Eclipse or ELF 3gun for single stage, TriggerTech or Geissele for two stage $250.

- Buffer Tube/Stock: Smoke Composites Rifle Length open stock $189.

- Buffer Weight: Standard Carbine weights removed $5, you can run this with the adjustable gas block for extremely low recoil/muzzle movement.  Also helps track shots through the scope when you get your optic.

- Buffer Spring: TTI Ultimate $19.

- Grip: Personal Pref, Magpul K2 is very light $19.





Total is just about ~$1800.  You could squeeze a Compass Lake Engineering Bartlein barrel in this budget, or go just slightly lighter with a V7 lithium or 2a Armament upper, and some V7 lower parts.


Let me know if you have any questions!

Thanks!! Email sent.

My 14.5 pencil barrel from faxon produced 1 moa results.

It's the fact that a lite barrel heats up a lot faster, it's the heat that opens up groups, but even hot, it's doesn't open up more then 3moa.

But it also cools off a ton faster.  

Then there is the velocity loss factor with shorter barrels, but like I atest, it will produce 1 moa results and doing so doesn't involve rapid fire so the heat thing isn't a huge deal.

Rapid fire is a cqb situation and what does moa matter when you engaging in close proximity? Your gonna hit the target.  I know the last thing I want is a heavy barrel that holds heat.

Good point but I've also seen plenty of guys use the stainless jp15 on the 3 gun courses and they definitely put a beating to their gun but itll still shoot moa or less and their rifle weigh about the same as my sr15, about 6 and change

Just curious - did you actually get this barrel yourself? Im trying to decide whether i want to pay the extra 70$ to get the socom barrel or just the regular light mid from lothar walther itself.

You'll notice everyone seems to either ignore your 18" requirement or the lightweight part.

I would pick an SPR build and try to have moderately lightweight parts.

Like an 18" Faxon Gunner barrel and a lightweight handguard, maybe lightweight receivers.  

I don't like lightweight BCG's, and even a lot of the receivers, as they just look weak.

If you want lightweight get a 14.7" pencil barrel, pin a flash hider to it, and build lightweight parts around that.

I have a heavier profile 18" barrel with a DD Lite Rail II 12.0 and a SOPMOD stock that I think balances nicely and I never have issues carrying it through the woods, FWIW.

I quite like the LW barrel potss mentioned though and if i combine that with a lightweight receiver set, the aim surplus bcg and the mft stock i should still ring up less than 7 lb. The other barrel choice is aWoa SDM 16inch.  What groups do you get with faxon and how is its durability?

I don't have a gunner barrel, but they get so many good reviews around here I wouldn't hesitate to buy one, and plan to someday.

The reason I mentioned the gunner over their pencil weight is because the weight difference is negligible in my opinion and the gunner was designed to be the best of both worlds.

A lightweight SPR build is going to be just that.  The best of both worlds.  You aren't going to get a super lightweight rifle with an 18" barrel, and you aren't going to get an SPR without an 18" barrel, that would just be a RECCE.  

Ah - missed the nomenclature. Guess what im really after is going for as much accuracy and as low a recoil as possible with a sub 7 lb ar. Doable?

here is my 18" spr build. Very few Ultralight parts and the total weight of the rifle unloaded is 6.8lbs and is balanced better than any other 18" ar I have used in the last 30 years. The troy tomahawk is a complete package with buffer and spring included at 10oz which is a good bit lighter than the battle link stock, carbine tube, spring and h3 buffer i originally had. The other benefit to using the Tomahawk is that with the 18" barrels spr profile the center of balance to the rifle was moved forward of the magwell. much snappier and swings quicker for me. You can see under 7 lbs before an optic is pretty easy to do with little money and still have reliable and quality parts.

As for accuracy, I am currently getting 1 moa using pmc x-tax 55gr but the paper work accompanying the barrel guaranteed 1/2 moa with 77gr match ammo. I am plenty happy with an inch @ 100. Its a rifle length system so it doesnt get any softer or cleaner shooting than that for direct impingement. You could opt for a comp such as the specwar if flash is not a concern for even less rearward force.

18" spr profile Rainier arms match rifle length 2.9 oz
Troy Tomahawk stock complete 10oz
13" BCM KMR
standard m4 forged upper and lower
Geissele 2 stage trig
FZ BCG
BCM Gunfighter CH
BCM mod 0 grip
A2 flash hider
magpul mbus ( poly)

Silly question - if I want to install an adjustable block the handguard has to be shorter than the distance to the gas block itself right? Also, does a rifle or midlength gas system require a rifle buffer?
Also - Rainier comes with test group sheet and submoa guarantee right?

Faxon is correct. I opted for the 13 just to save some oz and the rail length was all I needed.  You can go longer as long as you can reach in through the rail to adjust the gas block.

Why do you want an adjustable gas block on an 18" barrel ?

Yes the Rainier Arms barrel did come with the guarantee for 1/2" moa using match grade ammo and 77gr pills. It not a light barrel so the Faxon, BA Hanson or CBI would be lighter choices with the BA Hanson being closer to a spr profile @ 2.5 lbs I think.

Is adjustable gb not necessary on an 18 inch as its rifle length? Not sure why it wouldnt be helpful tho based on the balliatics.

I am no expert but if your using a rifle length system on a 5.56 i dont see a need for an adjustable gasblock. The need would arise if you were over gassed and needed to bleed some of the returning force/pressure.

The only thing an adjustable gas block will do for that build is add unnecessary weight.

Will it be necessary for the 16' middy from Lothar Walther? Was able to get in contact with their us ceo directly and he is gonna send me a PO :)

Id take a hard look at the Larue PredatAR barrels. They're pretty light weight and proven shooters.

If you feel like an 18" mid length would be too much the SLR rifleworks sentry 6 .450 spacing is a good match.

The Larue is $225 for standar ramps or $245 for m4 feed ramps.

With a good quality thin barrel I think you'll be fine. I wouldn't worry about it being less accurate when it heats up. Thin barrels will also cool faster.

The lothar walther barrel with a matching bolt and meloniting is 290 shipped and weighs 29 oz. Would the predatar be better?

I don't have experience with lothar so I can't give you a definite Larue>lothar or Larue<lothar accuracy.

What I can tell you is a 16" PredatAR barrel weighs about 24oz, and Larue barrels shoot lights out.

I took my 18" stealth out today and could consistently hit bowling pins at 500 yards. When I say consistently I mean 4 pins in 4 shots. 3 times in a row. I'd expect the PredatAR barrel to be no different.

Price wise, most common you'll have an upper with m4 ramps, so we'll assume $245 for the Larue barrel. The lothar is $290 with a bolt.

I found a stag arms bolt carrier with only a key for $65. So you'll need a firing pin, retaining pin, and cam pin. From stag that's $11 so $366 for barrel and bcg.

A standard complete bcg from stag is $115. That's $360 for a Larue barrel and bcg. $6 is basically negligible.

Now I could be wrong but a matched bolt basically just means they check headspace on the bolt for you. Given that most bolts and barrels will be in spec anyways (plus I have a set of 5.56 headspace gauges) so bolt matching doesn't really matter to me.

With the overall prices so close it's a toss up there. I don't have any experience with a lothar so I can't give you any indication of their accuracy. All I can tell you is that my Larue shoots, and many other people have been reporting the same.

Sorry I couldn't be more help.

I have the non-melonited Lothar Walther barrel.  Cost $199 and shoots <.5moa 5 shot groups with (expensive) factory ammo.  My moa challenge entry is on page 25.  The barrels are silly accurate, especially for the money.  They come in 18in as well in the light profile if you prefer that, you can get them straight from Lothar Walther.  

The Larue Stealth or Predatar aren't bad options either.  Best option is still have to Compass Lake Engineering spin you up a Bartlein or Kreiger in a light profile of your choice with a matched bolt, though it is also the most expensive option.

The Superlative Arms or SLR Rifleworks clamp on gas blocks will fit under many handguards.  Both companies provide their dimensions and most handguard makers do as well,  it is easy to check.  Ignore the ignorant fools saying you don't need adjustable, they have no idea what they are talking about.  Adjustable gas blocks let you run much lighter internals, decrease wear, increase reliability with a larger range of ammunition, and allow for less felt recoil and muzzle movement to easily track shots through your optic.  They also make reliable and pleasant function with a suppressor much easier.

That is fantastic to hear!  I actually emailed Lothar Walther and the CEO (Woody) emailed me back directly.  Was yours the 16 in or 18 in variety?  I'm very excited to put this together.  One more thing though - why SLR over Syrac?

Which receiver set would yall get?  I was thinking the 2A Balios Lite, but $500 is a lot to shell out for a receiver set.  Would the V7 forged set at around $260 be a better fit?

V7 makes very nice stuff, I wouldn't hesitate to use them.

I like the SLR because it is able to be taken apart, and it's almost impossible for the screw to seize up. The SLR also has district clicks where (I think it's the syrac, could be wrong) just uses set screws, and set screws can easily carbon weld themselves stuck.

Mine is the 16in poly rifles barrel, but for an apt I would go 18in. Really any forged upper/lower is fine, I just recommend what was very light.  Heck you can get an Aero set for cheap and only gain a few oz.  If your goal is the lightest ultra-light, the Balios or v7 lithium alloy are worth it.  Otherwise I would put that money towards the barrels, optic, suppressor, and ammo.

As for the gas block, I would go superlative arms actually as their bleed off design is quieter with a suppressor.  SLR would be my second choice, and as what I am currently using.

How much does the 18 inch weigh?

"Light weight barrels aren't accurate"

Here we go again....

Does superlative arms have a direct impingement gas block or is it only for a gas piston?

DI gas blocks.


And lightweight barrels can be accurate...for a little while....

Go with a 16" barrel. No reason to go with an 18" barrel over a 16". Its a proven fact that your only gaining around 50 FPS with an 18". And don't give me that crap about rifle length gas system and lowered recoil. Forget the 18".

If you do want to go longer then push it to 20" at least you get some significant gains in velocity with a 20" over an 18".

Also, to answer your question. Under 7 lbs? I don't think so. Under 8? Maybe, but not sure that you will be able to keep it under $2,000 as the lighter scopes and scope mounts bring a premium price.

EDIT: I just noticed this is before optics. Then yes its doable. But still, ditch the 18" barrel.