I've searched and see the VLTO MUR mentioned as a good upper, but no real consensus.

I plan to build a precision .223 AR.  This will be for 1-200 yds (so no need to mention other calibers).

I'm going to build it myself with a Lija/Bartlien/Shillen type barrel (so not looking for complete uppers).

What is considered the "best" upper?  I initially was thinking the LaRue stripped Stealth (Stealth)

I don't mind spending a bit on it to get a precise upper.

Would like to not have to true/lap but wouldn't mind if that's the best way to go (would be kinda fun and good excuse to get the tools, but this will probably be the only precision I build other than a bolt gun).  I understand with a "good" upper there is no need to lap as it would be machined "perfectly" and read  a post a long time specifically saying LaRue uppers don't benefit from lapping.

Is there an upper that is considered to be the "best" or most precise??????

I am a big fan of the Aero Precision M4E1 Uppers. The extension that the rail mounts to is integral to the upper receiver making the entire upper very rigid and strong, great for bipod mounts and such not making pressure POA/POI changes.

I've also heard the MUR is a good upper.  Also might check out San Tan Tactical.

LaRue Stealth would be an excellent choice.  Going along with that, why not just get their Ultimate Upper combo and be done?  Not taking away anything from Lilja or Bartlein, but bave you seen the accuracy of LaRue barrels?

Scroll down and look at the results.  
https://www.ar15.com/forums/precision-rifles/-ARFCOM-1-MOA-ALL-DAY-LONG-Challenge-/17-51/

The MOA all day challenge is a joke unfortunately and should under no circumstance be used as a guide to barrel accuracy.  2 of 3 top scores were recorded by known liars.  A few others are very suspect.  It was a great idea ruined by jackasses.

My stealth barrel is ok, but it is nowhere near the accuracy of Krieger, bartlein, or lilja in my experience.

OP, look at any of the billet uppers from known good manufacturers.  The VLTOR MUR is a great choice as are the mega arms/Zev offerings.  From what I've read and seen, the barrel extension fit is more consistent/tight and the threaded portion is more true (perpendicular to upper).  If you want to use a forged upper, the BCM M4 upper receiver has an extremely tight barrel extension opening.

Damn, dude.  "A great idea ruined by jackasses" and yet, setting aside opinions on certain accuracy claims, no one seems to be able to post up results equal to (or better than) those claims.  
I mean, if they're soooo much better, where's the proof?

BTW, there are several other barrel manufacturers in the Top 25, I was simply throwing out some options.  Or maybe they're all liars?...

Because some of the claims are ludicrous. When those shooters have been called out, they disappear or fail to substantiate their claim.  I don't know that they're repeatable unless you're handloading.

Sorry to gore your golden ox.  If you want to discuss excellent accuracy you've seen or evidence from well respected posters than I'm all ears.

Some users have reported excellent accuracy, others good or ok.  You can get the same results from other barrels at the $200 or less mark.

Stepping up to a jp, bartlein, Krieger, Hart, etc ensures you get a great barrel.  Whether that's worth the additional cost is up to you.  I wouldn't compare the stealth to those manufacturers.

Forged, I’d go with JP.

Billet, I’d go with either JP or Larue depending on which had the features I wanted.

Yeah, and several of those entries aren’t complete entries, I.e, they shouldn’t have been on the list to begin with! They don’t meet all of the criteria for a submission, and yet, the caretaker of the thread allows them to stay up. And, the end result is posters such as Repairman_Jack thinking they are the end all be all for barrels. Jack, It’s hard to legitimately outperform results that are believed to have involved some level of bending of the rules to obtain. I’ve got a few Larue barrels, I’ve witnessed or shot several others. None are my most accurate AR barrel. My Rainier Ultra Match barrels, even the lower grade Rainier match barrel has turned out better groups than my stealth barrel. That said, I think Larue makes good products. A Larue rifle or barrel could one day deserve to be at the top of the challenge list, but the top 2, perhaps 3 currently, do not deserve it.

OP
MUR receivers are very good, as are Seekins, Aero and BCM. Just stay away from receivers marketed as lightweight as they have thinner walls and may flex a bit more.

I'd tend to agree, there are some truly unbelievable groups posted to that thread, at least within the semi-auto division. Not that it's impossible with an AR, but it's incredibly difficult to achieve some of those results without a heavy sandbag up front or a full on bench-rest, and you'll likely be using an eared rear bag. I recently shot it, and the only reason I placed so high was because I had a single "miracle" group in the .2s which saved my overall score; otherwise I'd of been hovering around the 1" mark.

That said, that same Larue Stealth barrel will hover between around 3/4 MOA with handloads using a non MOA challenge compliant rear rest; I shot it the week after my MOA entry to confirm. It's a good barrel, but I wouldn't take the Pepsi challenge against a Bart/Kreiger for sure.

Again, my Larue barrel is good, but you do have to question things when Larue won't tell you anything about how they're made, the specs behind them, and they cost $250.

I'd love t see someone run a Hawkeye down one.

Edit: To answer the OPs question, I would a MUR or an M4E1 upper. You want an upper that's as thick as possible (definitely thicker than a Mil-Spec one).

I bought a cheap upper that I don’t even know the manufacturer, put a larue  barrel in it and am shooting 3/4 moa with a sig 1-6 on top and 70gr Barnes TSX rounds.  I consider that amazing for not spending a ton of money.

@rob78
whats "the stealth"?

Larue Stealth barrel.

First off, I never claimed they were the "end all, be all" for barrels.  Just that they were a good option to consider as well.  
Secondly, bending of the rules aside...those barrels shot those results.  Does more wiggle at the back of the rifle make the barrel any more or less accurate?  No.  
That was my point about it's as much the Indian as the arrow when it comes to truly long range precision.  And yes, a great deal of the time long range precision uses tailored handloads to further minimize variables that affect groups.  
What evidence do I have (other than all those targets posted up in MOA All Day that you've completely disregarded)?  How about the test targets that LaRue ships out with every single one of their complete rifles?  
All of them are under MOA or the rifle doesn't ship.  The vast majority of those are well under MOA.  
Do Bartlein, Shilen, or Krieger barrels ship with proof targets?  I'm assuming I disregard any results I might see posted in the shooting thread.  After all, who know how they had their rifles bagged up.

Finally, I agree the MOA All Day thread isn't the absolute measure of a barrel's true potential.  Rather it is a measure of a shooter's true ability.  (At least it's supposed to be)
But until someone takes a shitload of different barrels and bolts them to a 10-ton mechanical shooting rest with zero movement, I'm guessing we're gonna have apply some sort of measuring stick.  
So what do you suggest?  Besides "Trust me Bro, the $800 custom-twist barrel with the OCD break-in schedule is soooo much better than the other guys".

You guys are long on criticism and short on solutions.  The same type of fuckers that ran MOLON off his ammo accuracy thread with the incessant nitpicking of results.  
And then you have the audacity to tell me I've got some sort of golden ox?  I'm not the one that came out shitting on other people's results, especially over questions that have been asked and answered in the Challenge Discussion Thread.

So there you go, OP.  You can either trust what you see or you can trust what you hear.  You've damn sure got some opinions on the matter, now.  

Here's a couple more opinions.

Buy a quality barrel and try it out.  If you don't like it, sell it on the Equipment Exchange and pick something else.  Barrels are easy to swap.  
To achieve any barrel's absolute true potential, you're gonna have to handload and work up an accuracy node that works "best" with your barrel.  
Second best is to buy several different brands of off-the-shelf match ammo and bullet weights and see what your rifle likes.

Aero M4E1 upper - Good  
UCWRG (Umbrella Corp) upper - Excellent (scarce as hen's teeth)  
Faxon Firearms Barrels - Good to excellent.  They've just come out with a Match Series barrel line that should be worth checking out.

Jesus dude.  The point is, don't use the MOA challenge as a barometer of barrel accuracy.

You're awfully worked up over this.  

Larue barrels are ok.  Mine is just Ok, as in shoots to about an MOA.  I own one as do others that have posted in this thread.  I think they're awfully overhyped by a few folks.  Odin works, Faxon, Ballistic Advantage also shoot as well for a little less money.  Not that it matters because the OP only asked about uppers, but you felt the need to push a barrel manufacturer that you somehow "feel" is the equivalent to the match barrels he intends on using.

Took my stealth out today. Tried about 9 different loads with it. Had one group print .60 moa (6shots) and another print .73moa (5 shots). The .60moa group was a pleasant surprise, as that’s probably the best 5+ shot group I’ve gotten out of this barrel. They all seem to be in the .6-.9moa range. Which, is good performance for the price. Maybe it’s coming into its own now and will improve in group size.

MEGA Billet!

Currently being sold at JSE Surplus under the following description "AR-15 SBU Billet Upper without Side Charging Handle Slot– JSE EXCLUSIVE"

A few bucks cheaper at Rainer
Mega Billet

What about the LMT MRP uppers?

I understand that a conversion in required to adapt a standard AR15 barrel for the MRP, but if we took a high quality barrel and installed it in the MRP, how might it compare to some of the other options discussed?

First, as already mentioned, I wouldn't use the MOA All Day list as an indicator of quality uppers. Mike_P and dpmmn have a history of integrity issues; that's 4 of the top 9 submissions in the SPR division. I believe InfiniteGrim (#27 on the SPR listings) was banned for a less than honest EE ad.  Although his entry isn't suspicious, it brings his integrity into question.  In short, there are just too many entries in the MOA All Day thread which are suspect by themselves and/or submitted by people who have a questionable track record of honesty for me to use it even as anecdotal evidence of any specific part leading to better accuracy or precision over a competing product.

That's a shame too, because I am sure the vast majority of entries were submitted by good, honest people.

Also, the listings make no note if the uppers were trued and lapped.  Personally, I'd rather have a budget upper that has been trued/lapped professionally over even a factory "premium" upper that has not received that treatment. If I were you, I'd go that route.  Get a solid upper (Aero, Colt, BCM, anything with a Cerro Forge mark) and get it trued and lapped. That's where you will get any accuracy improvement out of your upper.

Thanks, good information.  I'll probably go billet (and would lean to VLTOR/Aero) and look for the heavy construction choices.  I'll probably lap it just to be sure.....

For my latest build, 224 Valkyrie, I ended up going with  another Hogan (I.E. POF) receiver.  I almost went with a Vltor as I was using a Seekins lower.  Reason I went with the Hogan receiver is  mostly cause I've been using their build kits for majority of my rifles in the past (last 6 builds).  I use to lap their receivers, more like attempt, but when I would do it, they were always spot on, so I was just wasting my time.  I cant comment if POF receivers are the same or not.  But since Hogan is very close to me (pof is about a 45 min drive), that's why I use them.  That and they usually give me a decent price on it.

That being said, this will prob be my last time using their receiver.   Not cause of any "issues" but more so cause of the proprietary rail they use.  *POF has since gotten away with this and uses reg receivers / rails now.  I'm able to use the 14.5" rail (or the 9" or 11") but I do like to have options.   Next build I'll prob use the Vltor

I'd use a Mega Arms megalithic(quad rail style) upper with an 18" RL mid-profile and nitrided LW50 barrel.

Can you tell I'm always wanting to do another build?

Must resist...

I like the LaRue Stealth upper since the handguard does not touch the barrel nut at all.

For a precision AR15, I'm of the mind that there are more options now in components that are more than suitable.

Instead of worrying about the components as a focus, I personally look at how the fit is of the barrel extension to the upper extension tunnel.

I start with a trued receiver face, and will build up the inside of the tunnel with Cerakote for a super-tight fit, and still will bed the extension into the tunnel.

The barrel quality and bore-to-OD concentricity, as well as thread concentricity to bore are probably the biggest factors in accuracy.

The gas block fit, gas tube bedding, torque, muzzle device torque, and several other things can really tighten up your harmonic balance across components.