Larue Ultimate Upper Build Advice

[eugevita]

Greetings! I am planing to purchase a Larue Ultimate Upper kit but was hoping to get some feedback/advice from the Larue/semi-auto experts here before I pull the trigger. I am fairly seasoned with precision bolt guns but this will be my first semi auto precision build so definitely looking to get some thoughts.

My original plan was to get the kit in 6.5 grendel with the purpose of using it as a plinker out to 1000 on steel and hunting whitetail deer and pigs as a secondary role. Also thought I might re barrel it later in 6ARC if that takes off since I would already have the bolt and mags. I am now having second thoughts about this due to the ammo situation, I do not reload and cannot find anything other than wolf 6.5 grendel ammo in stock. As much as I want a grendel it is kind of unsetting to get into a new caliber during this time.

The other option I am considering is getting the upper in 5.56 with either a 16" or 18" stealth barrel and setting it up as a spr style rifle. While 5.56 is expensive as hell currently it is at least widely available and I have another AR in 5.56. Biggest con I see here is knockdown power, I know I could still shoot deer with 5.56 but it certainly is not ideal. I am thinking stealth barrel as it should be more accurate for longer strings of fire compared to the predatAR? Does 16" vs 18" really make a big difference when shooting 77gr out to distance?

The final option is getting the AR 10 upper kit in 308. This rifle would have plenty of power and I already own a 308 bolt gun so it would not be a new caliber for me and 308 is still relatively available. The cons here are increased weight and several hundred bucks more than the AR-15 kit. Does anyone know what the weight difference is between the 308 AR-10 vice the Larue AR-15 on average?

I plan to buy a larue factory stripped lower to use with this kit.

Really appreciate everyone's thoughts/advice as I work on choosing one of the above options.

 

[houndog]

So, as someone who owns 3 LaRue uppers and a 6.5 grendel upper, I'll take a shot at this.

First, I have something of a personal bias against the 6.5 grendel cartridge. I bought one of the earliest uppers (Alexander Arms not from LaRue) and the thing has never fed worth a damn - despite using several different mags and ammo from different companies. And you're right I think ammo availability (and price) will be an issue if you don't reload. Also, not the cartridge I'd choose if my primary use was plinking steel out to 1000. Having said that, the cartridge has now been around a while and I think they've got most of the feeding issues solved and it would make a decent hunting round out to around 3-400 yards.

Second, 5.56 upper (whether 16" or 18") is not really a good choice for either hunting or shooting out to 1000, so I'm not sure I'd really go this route either. Yes, ammo will always be plentiful (and hopefully will once again be cheap), the rifle will be relatively light, and recoil will be minimal. If you didn't want to hunt and most of your shooting will be no further than 600 yards this would be a good choice and a pretty versatile cartridge. But given your intended use, it will be a compromise.

Third, a large frame AR will be heavier, more expensive, have more recoil, and in my experience will be tougher to shoot well. Even though you have some experience behind a bolt gun, you're going to have a pretty steep learning curve to shoot a semi-auto with precision. That learning curve will be even steeper with a large frame AR. However, if you want to hunt and shoot out to 1000 I think this is probably the way to go.

Fourth, even though you already have a .308 bolt gun and ammo will always be plentiful, you might want to consider switching to 6.5CM, particularly for long range shooting. The round has significantly better ballistics, particularly beyond 7-800 yards and less recoil (which will be important if you are shooting without a spotter and need to be able to see your misses). Moreover, before Covid hit ammo was generally available and the Hornady factory stuff is very good. Even their American Gunner brand - which used to be around .80/rd - was capable of around 1 MOA in my LaRue upper.

Finally, if you do get a large frame upper from LaRue and you think you might ever want a suppressor, they have a great deal going and even though you will have a LONG wait, you can't beat the price.

 

[eugevita]

So, as someone who owns 3 LaRue uppers and a 6.5 grendel upper, I'll take a shot at this.

First, I have something of a personal bias against the 6.5 grendel cartridge. I bought one of the earliest uppers (Alexander Arms not from LaRue) and the thing has never fed worth a damn - despite using several different mags and ammo from different companies. And you're right I think ammo availability (and price) will be an issue if you don't reload. Also, not the cartridge I'd choose if my primary use was plinking steel out to 1000. Having said that, the cartridge has now been around a while and I think they've got most of the feeding issues solved and it would make a decent hunting round out to around 3-400 yards.

Second, 5.56 upper (whether 16" or 18") is not really a good choice for either hunting or shooting out to 1000, so I'm not sure I'd really go this route either. Yes, ammo will always be plentiful (and hopefully will once again be cheap), the rifle will be relatively light, and recoil will be minimal. If you didn't want to hunt and most of your shooting will be no further than 600 yards this would be a good choice and a pretty versatile cartridge. But given your intended use, it will be a compromise.

Third, a large frame AR will be heavier, more expensive, have more recoil, and in my experience will be tougher to shoot well. Even though you have some experience behind a bolt gun, you're going to have a pretty steep learning curve to shoot a semi-auto with precision. That learning curve will be even steeper with a large frame AR. However, if you want to hunt and shoot out to 1000 I think this is probably the way to go.

Fourth, even though you already have a .308 bolt gun and ammo will always be plentiful, you might want to consider switching to 6.5CM, particularly for long range shooting. The round has significantly better ballistics, particularly beyond 7-800 yards and less recoil (which will be important if you are shooting without a spotter and need to be able to see your misses). Moreover, before Covid hit ammo was generally available and the Hornady factory stuff is very good. Even their American Gunner brand - which used to be around .80/rd - was capable of around 1 MOA in my LaRue upper.

Finally, if you do get a large frame upper from LaRue and you think you might ever want a suppressor, they have a great deal going and even though you will have a LONG wait, you can't beat the price.

Thank you very much for the detailed response, I greatly appreciate the info!

Your comments on both Grendel and 5.56 options make sense, guess I need to keep pondering this. If the grendel ammo was more available I think it would be the clear winner. Going to query my local stores and see what the grendel situation is like these days.

Regarding the AR-10: I called Larue and it sounds like it is on average 1.6-1.7lb heavier than an AR-15 with 18" barrel. I fully agree with your point about the AR-10 in 6.5CM. That said, I already have a 6.5. currently getting built at bugholes (origin action with proof barrel) and I am already worried about how I will source ammo for this rifle. I too am a big fan of Hornady Gunner, really miss being able to buy that stuff for .80 a round! In addition to ammo I am not keen on an AR-10 in 6.5 due to barrel life, this is the big pro of 308 in my eyes.

Thank you again for the insightful response!

 

[houndog]

Can't argue with you about barrel life of .308 vs. 6.5CM, and although I'm not a hunter .308 is probably the better round for that as well. Plus with .308 you also have the option of surplus military ammo for plinking which used to be both cheap and plentiful, and hopefully will eventually become available again - although the days when I was able to purchase a couple of thousand rounds of surplus Australian .308 (which was of very high quality) for .17-18 per round are long gone.

 

[LRRPF52]

You can order cases of anything you want right now that is common, including Grendel. Prices are more than double and triple with popular cartridges. I see 6mm Creedmoor at all the LGS shelves, while everything else is pretty much gone. I saw 3x 200rd cases of 6.8 SPC at Sportsman’s Warehouse today for normal price. Last time I was there they had several 200rd 6.5 Grendel cases of Hornady American Gunner, but they’re out of stock now.

Stuff shows up, but just sells quickly.

The best all-around cartridge that fits in the AR-15 that is widely-supported is 6.5 Grendel since you have everything from steel case on up to Federal Gold Medal Match. Last I counted, there were 98 factory loads and that was earlier this year.

Feeding: I’ve been shooting 6.5 Grendel since 2009 regularly and in significant volume, across a wide range of barrel and gas system lengths with various types of factory and hand-loaded ammunition. I can recall maybe 2 FTFeeds over the last 11 years. One was that discontinued awful PPU/Wolf import 123gr Soft Point. The other was with a pre-production Elander 17rd magazine and one of my longer COL A-MAX hand loads that seems to have hung-up on the front wall of the mag and caused a nose-dive.

Everything else has just run. The 12” CLGS with Bootleg carrier suppressed seems to run with the most authority, like a raped ape.

Tiny fraction of some of the ammo samples I’ve shot:

More importantly, I’ve seen a lot of different people come to courses with Grendels and not have feeding issues, to include shooting higher volume with CLGS suppressed with steel case from the 24rd mags.

But as far as cartridge goes, whatever you can stack deep that works for your needs will work.

If that’s 7.62x39, 7mm-08, or something odd and you have it, so be it.

Look at ammoseek for ordering online.

 

[S197]

For the money that larue wants, there are a lot of better options available. if you wanted to stay on the basic ar15 platform you could use a 6.8 spc, 6.5g and of corse 556. i would talk with Georgia Precision and jp enterprise , would be a better investment if you decided to sell. there was a lmt 6.8, 5.56 ready to run kit in the px for 2000.00 the other day.

 

[houndog]

S197 - don't want to get into a p*ssing contest with you, but don't really agree that LaRue's are over-priced. I don't have personal experience with either GP or JP Enterprise, but from everything I've read they make outstanding rifles. However, a quick google search indicates that to get an AR10 from them is going to run you at least $3500. If you get a LaRue UU kit and their billet receiver you can put together an AR10 for about $1600. So you could buy 2 LaRue's for the price of a GP and still have some money left over. Or you could buy a LaRue AR10, add a LaRue suppressor and buy a LaRue AR15 for about the cost of a GP or JP Enterprise. Are the latter better rifles? I suspect they probably are. Will they sell for more used? They better, they're more than double the price. And no, I have zero affiliation with LaRue, but I do think they make a very good product and have a well deserved reputation for accuracy. And unlike my 6.5 Grendel upper, they have been 100% reliable from day one.

LRRPF - I admit I am a sample of 1. However, I was one of the first guys to buy a 6.5 Grendel upper from Bill Alexander, and all I can tell you is I was not alone - a bunch of initial purchasers experienced problems. As I recall people were bending the feed lips of mags, dremeling, etc. to try to fix the problem. Sounds like they rectified the problem after the first few batches were released. However, mine is one of the few rifles I have never been happy with. I would be more than happy to post pictures of rounds where the bullet was driven back into the casing and failed to feed. And if you would like to buy my upper, I would be happy to sell it to you for what I paid for it. It doesn't have a lot of rounds through the barrel.

 

[eugevita]

You can order cases of anything you want right now that is common, including Grendel. Prices are more than double and triple with popular cartridges. I see 6mm Creedmoor at all the LGS shelves, while everything else is pretty much gone. I saw 3x 200rd cases of 6.8 SPC at Sportsman’s Warehouse today for normal price. Last time I was there they had several 200rd 6.5 Grendel cases of Hornady American Gunner, but they’re out of stock now.

Stuff shows up, but just sells quickly.

The best all-around cartridge that fits in the AR-15 that is widely-supported is 6.5 Grendel since you have everything from steel case on up to Federal Gold Medal Match. Last I counted, there were 98 factory loads and that was earlier this year.

Feeding: I’ve been shooting 6.5 Grendel since 2009 regularly and in significant volume, across a wide range of barrel and gas system lengths with various types of factory and hand-loaded ammunition. I can recall maybe 2 FTFeeds over the last 11 years. One was that discontinued awful PPU/Wolf import 123gr Soft Point. The other was with a pre-production Elander 17rd magazine and one of my longer COL A-MAX hand loads that seems to have hung-up on the front wall of the mag and caused a nose-dive.

Everything else has just run. The 12” CLGS with Bootleg carrier suppressed seems to run with the most authority, like a raped ape.

Tiny fraction of some of the ammo samples I’ve shot:

More importantly, I’ve seen a lot of different people come to courses with Grendels and not have feeding issues, to include shooting higher volume with CLGS suppressed with steel case from the 24rd mags.

But as far as cartridge goes, whatever you can stack deep that works for your needs will work.

If that’s 7.62x39, 7mm-08, or something odd and you have it, so be it.

Look at ammoseek for ordering online.

thank you for sharing your grendel experience, I appreciate it!

ammoseek is a go to site for me, check it daily

 

[eugevita]

For the money that larue wants, there are a lot of better options available. if you wanted to stay on the basic ar15 platform you could use a 6.8 spc, 6.5g and of corse 556. i would talk with Georgia Precision and jp enterprise , would be a better investment if you decided to sell. there was a lmt 6.8, 5.56 ready to run kit in the px for 2000.00 the other day.

i know JP and GAP make great stuff! That said you would be hard pressed to beat the price of an ultimate upper!

 

[LRRPF52]

S197 - don't want to get into a p*ssing contest with you, but don't really agree that LaRue's are over-priced. I don't have personal experience with either GP or JP Enterprise, but from everything I've read they make outstanding rifles. However, a quick google search indicates that to get an AR10 from them is going to run you at least $3500. If you get a LaRue UU kit and their billet receiver you can put together an AR10 for about $1600. So you could buy 2 LaRue's for the price of a GP and still have some money left over. Or you could buy a LaRue AR10, add a LaRue suppressor and buy a LaRue AR15 for about the cost of a GP or JP Enterprise. Are the latter better rifles? I suspect they probably are. Will they sell for more used? They better, they're more than double the price. And no, I have zero affiliation with LaRue, but I do think they make a very good product and have a well deserved reputation for accuracy. And unlike my 6.5 Grendel upper, they have been 100% reliable from day one.

LRRPF - I admit I am a sample of 1. However, I was one of the first guys to buy a 6.5 Grendel upper from Bill Alexander, and all I can tell you is I was not alone - a bunch of initial purchasers experienced problems. As I recall people were bending the feed lips of mags, dremeling, etc. to try to fix the problem. Sounds like they rectified the problem after the first few batches were released. However, mine is one of the few rifles I have never been happy with. I would be more than happy to post pictures of rounds where the bullet was driven back into the casing and failed to feed. And if you would like to buy my upper, I would be happy to sell it to you for what I paid for it. It doesn't have a lot of rounds through the barrel.

There was a lot of back-and-forth with C Products on mags in the beginning. What mags do you have?

What upper do you have?

When I build an upper, I de-edge, blend, and polish the feed ramps no matter if large or small frame, or chambering.

No matter what cartridge, I vet my magazines to see which ones work and which ones don’t. That includes pistols and other types of actions.

I have found at least 2 out of 20 Grendel mags that are defective, including one with a body that is pushed-in or crushed somehow. I remember an older ASC mag that had one feed ramp perpendicular to the vertical axis, and the other lip correctly oriented for a slight upward feed angle of the cartridge.

Most CProducts and Elander mags have been fine though. There is a CProducts 15rd mag that looks like a 5.56 20rd in size that was never supposed to be made, since it doesn’t have a curve to the body. Bill A. rejected those pallets of mags since he had asked for a curved body.

Elander 17rd mags have the first curved body that is about the size of a 20rd mag, and they didn’t exist when Grendel was introduced. They’ve only been around since 2014 if I recall.

I bet I could square your upper away though. If you have nose-diving rounds smashed into the case, that’s almost always magazine-related. I haven’t seen that type of malfunction in 6.5 Grendel in a long time across a wide variety of guns. With feed ramp work and known-performer mags, I bet the problem would disappear.

Regarding value of the LaRue UU kit. There isn’t a better deal around right now. You can built a complete billet AR-15 rifle from a very reputable company for half the price of many other rifles that are still using forgings, many of whom precious few have heard of. The UU upper-to-handguard interface is extremely rigid as well, totally isolated from the barrel and barrel nut.

 

[RUTGERS95]

1600 for a complete large frame LaRue sounds pretty good to me. Lots of value in that 1600 but if looking for real value, get the Aero M5 around 1100. That said, I'd buy, and did, the LMT MWS and call it a day. Now I have 2 and couldn't be happier. Obviously you can change calibers, get accuracy, reliability etc but 1 weapon to spread the calibers

 

[houndog]

LRRPF - Thank you for your comments. I do have one of the early Alexander Arms uppers. Mags are probably early C-Mags, and yes, as I recall there were a lot of discussion about the mags being problematic - hence the bending of feed lips, etc. I might try an Elander mag (although living in CO it will need to be 15 rounds or under).

Also, in fairness to Alexander Arms - I never really pushed it with them. Their initial response was "it's bad mags, not the upper". Should probably try a couple of more mags, particularly since there's a wider selection now, and if I still have problems insist that Alexander Arms take a look at the upper. I think you're right this problem is fixable.

 

[longshot2000]

LaRue builds a quality gun. Personally, I have built Mark’s kit and am extremely disappointed in the design. Engineering and shooting is solid. The rear take down pin area on the 556 was a mismatch between a fantastic functional and aesthetic design I the lower and upper that had lines that just did not come together. It was like two different manufacturers did the design work. The rail to receiver interface is bauhaus functional, solid and ugly. Not sure if the large caliber has changed but small caliber has Keymod rail. Who is not making MLOK?

All of this is acedemic. Because, I would likely ask you to consider other brands, like LMT. But, thise are pretty much not available.

In the large caliber, I personally own two LaRue OBRs and a hybrid Predator something. Both are awesome.

The build kit will get you a solid gun, but take a look at the other LaRue guns, which I think are superior in build and aesthetics and design.

 

[LRRPF52]

You can order billet LaRue lowers to match with the upper.

My complete Stealth 2.0 rifle is one of the most solid-feeling AR-15s I’ve ever felt. It just feels like one single unit. The receiver mate is built like a vault.

 

[Triple D]

You can order billet LaRue lowers to match with the upper.

My complete Stealth 2.0 rifle is one of the most solid-feeling AR-15s I’ve ever felt. It just feels like one single unit. The receiver mate is built like a vault.

That is likely the exception and not the rule, at least with the UU kits. My large frame UU has play between the receiver as does my SF UU kit. This has been reported by quite a few ppl as well. The SF lower does lockup solid with Vltor MUR upper receivers though (3 of mine). An accuwedge may be needed for the LT receivers to get them solid.

I like the rail to receiver interface, and I think the large frame UU kits are a good value for a one stop shop. The upper is rigid and the system has low recoil. The 22” Larue UU 6.5creed build averages around .7moa with handloads so I’m not in a hurry to replace that barrel just yet. It will likely get a BA 6.5creed barrel when that time comes, because my Aero/BA build is a bit more precise than the LT kit.

Admittedly I’m not a big fan of the 6.5grendel, but I pulled the 6.5grendel barrel on my UU kit because it wasn’t consistent. Some good groups, but most were in the 1-1.25moa range. Handloads got down closer to the .5-.6moa range, but after a few rounds they would open up. I replaced the barrel and bolt with a 223wylde budget barrel and it averaged sub 3/4moa over 25rds during load confirmation using a pet load for other barrels.

TLDR: The upper receivers and rail interface is great with the LT UU kits. The receivers may not have a rock solid lockup. The barrels are useable and meet the needs of a lot of shooters, but may need replacing if you want to get more precision from the platform. I don’t think his current in house barrels are on the same level as the L-W barrels that were used to build their reputation for precision. Some are certainly good, and some are great, but I think the really good ones are going into the factory guns and not the UU kits.

 

[eugevita]

You can order billet LaRue lowers to match with the upper.

My complete Stealth 2.0 rifle is one of the most solid-feeling AR-15s I’ve ever felt. It just feels like one single unit. The receiver mate is built like a vault.

Indeed I plan to order this lower!

 

[eugevita]

LaRue builds a quality gun. Personally, I have built Mark’s kit and am extremely disappointed in the design. Engineering and shooting is solid. The rear take down pin area on the 556 was a mismatch between a fantastic functional and aesthetic design I the lower and upper that had lines that just did not come together. It was like two different manufacturers did the design work. The rail to receiver interface is bauhaus functional, solid and ugly. Not sure if the large caliber has changed but small caliber has Keymod rail. Who is not making MLOK?

All of this is acedemic. Because, I would likely ask you to consider other brands, like LMT. But, thise are pretty much not available.

In the large caliber, I personally own two LaRue OBRs and a hybrid Predator something. Both are awesome.

The build kit will get you a solid gun, but take a look at the other LaRue guns, which I think are superior in build and aesthetics and design.

Thank you for the feeback, I do believe the current kits come with MLOK handguards!

 

[eugevita]

Thank you for all the thoughts and happy thanksgiving!!!

So I made my decision!

Yesterday the ballistic advantage 6MM ARC barrels came in stock on brownells and I ordered the 18" SPR profile. There was also a lot of 6 ARC ammo in stock on ammo seek yesterday so I took it as a sign and ordered 320 round of 108ELDM at 1.22 a pop.

Plan to order the larue billet lower tomorrow as well as the ultimate upper kit in 6.5 Grendel! My plan is to replace the included 6.5 grendel barrel with the ballistic advantage 6ARC barrel and to essentially have a Larue build AR in 6 ARC.

I talked to Larue and it looks like I will just need to buy a rifle length gas tube to accommodate the new barrel as well as a low profile adjustable gas block if I dont want to run the non adjustable that is included in the kit.

Anyone have any thought on how critical an adjustable GB is for this build? I plan to initially run the rifle without a can but may suppress it later on. I am inclined to go adjustable but having never tinkered with one before I am a little worried about having a more complex system lol

Also will need to figure out which 6 ARC mags to use. From my preliminary research on the 6 ARC thread it sounds like the C Products Duramags have been used with some success. Any 6 ARC people here?

I gambled a bit with pulling the trigger on the 6 ARC components but I am pretty excited about the build!

 

[Animal357]

I will disagree that LaRue is overpriced as well. You get what you pay for. I have owned two 308s that shot 1/2" with factory ammo and a 5.56 that shot 3/8"

 

[RUTGERS95]

so this thread has me thinking of a 5.56 kit from them but in 308, I stick to LMT.

 

[Halfnutz]

A few years old.
6.5CM UU Kit
The barrel to upper fit was sloppy and required shimming to tighten things up.
Upper to lower fit luckily is tight on mine. I think they should add a tensioning screw since they aren't matched sets. I waited a while to get the lower.
The Magpul stock required a longer buffer tube from LaRue, not listed on thier website but available if you call. It still uses a carbine length buffer/spring.
FDE no longer available (currently).
Did come with a high pressure bolt. The chromed BCG cleanes up quickly. Contact areas are polished. (Not sure they are doing this anymore).
Ran a Geissele Hi speed match at first, switched back to the MBT.
Hovers around 1 MOA sometimes better for me with Hornady AG, Match, Federal GMM, and the FGMM/Berger. Using an Atlas Bipod and a rear bag vs the monopod and harris made a difference for me.

 

[LRRPF52]

Thank you for all the thoughts and happy thanksgiving!!!

So I made my decision!

Yesterday the ballistic advantage 6MM ARC barrels came in stock on brownells and I ordered the 18" SPR profile. There was also a lot of 6 ARC ammo in stock on ammo seek yesterday so I took it as a sign and ordered 320 round of 108ELDM at 1.22 a pop.

Plan to order the larue billet lower tomorrow as well as the ultimate upper kit in 6.5 Grendel! My plan is to replace the included 6.5 grendel barrel with the ballistic advantage 6ARC barrel and to essentially have a Larue build AR in 6 ARC.

I talked to Larue and it looks like I will just need to buy a rifle length gas tube to accommodate the new barrel as well as a low profile adjustable gas block if I dont want to run the non adjustable that is included in the kit.

Anyone have any thought on how critical an adjustable GB is for this build? I plan to initially run the rifle without a can but may suppress it later on. I am inclined to go adjustable but having never tinkered with one before I am a little worried about having a more complex system lol

Also will need to figure out which 6 ARC mags to use. From my preliminary research on the 6 ARC thread it sounds like the C Products Duramags have been used with some success. Any 6 ARC people here?

I gambled a bit with pulling the trigger on the 6 ARC components but I am pretty excited about the build!

Get a Bootleg adjustable carrier instead.

I’ll never buy an adjustable gas block again after what the Bootleg does for me in suppressed builds, or MLGS 18” guns that need the gas dialed down sometimes.

 

[eugevita]

Get a Bootleg adjustable carrier instead.

I’ll never buy an adjustable gas block again after what the Bootleg does for me in suppressed builds, or MLGS 18” guns that need the gas dialed down sometimes.

Thanks, will have to check it out, never heard of it before, seems cool