Tested four different barrels for my LMT 5.56mm MRP today, unscientific findings inside with photos

[matt33]

Several months ago, I bought a LMT MRP 5.56mm rifle during a Black Friday sale. I'm a bit of an accuracy enthusiast with AR rifles, but I also like a practical weight carbine suitable for general use.

Over the past several months, I purchased 4 different barrels for this rifle, I figured I would share my results as it might be helpful to others. I spent considerable time with each barrel over the months, each one has at least 200 rounds downrange. Today's results were fairly representative of my more extensive testing with each barrel.

Today, I fired two 5 round groups at 100 yards with each barrel, except the Bartlein barrel as this is the primary barrel I use and it has already proven to be extremely accurate. I only fired one group with the Bartlein barrel to re-zero the scope as it was getting dark. I was going to use a 32x nightforce scope for this test, but I was pressed for time, so I used the vortex 1-10 razor that lives on this rifle. All shots felt pretty good, I don't think there was much in the way of shooter error. Ideally I would have used 10 round groups, but again I was pressed for time.

All groups were fired using handloads consisting of 73 grain Berger bullets and IMR 8208. This particular load shoots as well as anything I've tried in every AR I own.

First up, the factory LMT 16 Chrome lined Barrel. This produced groups measuring 1.53 and 1.72, velocity was 2,573 with an extreme spread of 50 and SD of 15.9

Next up was the most disappointing to me, this is an $800 Factory LMT 5r cut rifled 16" barrel. I spent considerable time with this Barrel when I bought it, it is frustrating because it wants to shoot better, but it almost always throws a shot in every group.

Next up are two barrels that I had D Wilson convert, I'm very pleased with both of them. The first is a Daniel Defense 14.5 heavy SOCOM profile carbine length CHF Chrome lined barrel. This thing consistently hovers at or just under 1 MOA. Ejection is at 3 o'clock, it's gassed really well for a fighting carbine. Groups were .837" and .973" ( ignore the upper right target, I shot this unsupported as I was just getting on paper)

Lastly, I re-zeroed the Bartlein barrel that I primarily run, probably pushing 1,000 rounds through this Barrel at this point. It consistently puts five rounds between .3" and .75", with numerous 10 round groups that have been in the .6's. The first cold/very clean barrel shot went slightly high, the next 4 went into .347", group size was .744" . It's worth noting that the Bartlein barrel was much faster than the 16" LMT factory barrels, 2,680 FPS, vs. an average of 2,580 FPS for the two 16" factory LMT barrels that I shot today.

All groups were shot with a Vortex 1-10 razor, not the best optic for shooting groups, but it's very practical and it works great for the type of shooting I do. Here are some additional photos showing the barrels, rifle, stuff like that

 

[db2000]

The problem is LabRadar is obsolete

 

[matt33]

This labradar has lived a tough life. I keep meaning to get one of those Garmins, but remarkably this thing still works.

 

[unclemoak]

Thanks for the sharing your findings.

 

[CaptArab]

Thanks for posting.
I've considered taking the dive into this platform. Kinda confirms a custom tube is needed for what I want it of it.

 

[matt33]

Thanks for posting.
I've considered taking the dive into this platform. Kinda confirms a custom tube is needed for what I want it of it.

Yes, the platform itself is outstanding, but I wasn't able to achieve the level of accuracy I wanted from OEM barrels.

Fortunately, D Wilson can convert any AR barrel for a reasonable price in a reasonable time. I'm very happy with both conversions he did for me.

The Bartlein barrel hammers, and the Daniel Defense 14.5 is solid too. I run the DD when I am shooting primarily inside of 300, and especially when training up close with a lot of high volume fire. I don't feel guilty about burning that thing down.

Here’s a 10 round group with the Bartlein:

 

[PBWalsh]

@matt33

Have you ever tested POI shift from bipod/bag to barricade/tripod?

 

[matt33]

@matt33

Have you ever tested POI shift from bipod/bag to barricade/tripod?

I have, there is virtually none that I've been able to measure out to 300. That's one of the main things I like about LMT, I love absolutely everything about the rifle, except the accuracy with OEM barrels. The Ambi lower receiver is my favorite lower on the market, and the monolithic upper is my favorite upper receiver/ rail combo on the market. The factory trigger was not terrible, but I did replace it with a Geissele SSA-E

I knew going in that I probably was going to upgrade the chrome lined factory barrel anyway, so it wasn't a huge disappointment. I was pretty disappointed with the factory cut rifled barrel that I bought separately. It is barely more accurate than the factory chrome lined barrel, and costs these same as a Bartlein or Krieger.

I will say this about the factory cut rifled LMT barrel, it shows some promise. It's kind of like a hot girlfriend that is relatively not crazy most of the time, but 20% of the time she goes nuts for no reason.

I think if I spent another few hundred rounds with it, it would probably become close to 1 MOA. One of the last groups I shot with it was a 10-round group at 100 yards, the first 9 rounds went into .89", but then the 10th round flew 1.5 High from the rest of the group. I finally threw my hands up in the air and ordered a Bartlein barrel from Craddock Precision the next day. My large frame 6.5 LMT 20" SS Barrel was kind of the same way. It was probably mostly me getting used to the large frame ar, but it seems to have started shooting noticeably better after several hundred rounds. Annoying. At this point, it shoots 130 Berger Hybrids sub MOA every time I put it on the bench.

 

[PBWalsh]

@matt33

Thanks for the reply. Found another thread of yours showing a 5 round group from a bipod and tripod with little to no difference in POI. I appreciate it!

 

[RIGREG]

@matt33
How are the gas tubes on the D.Wilson conversions held in alignment, or fixed, at the receiver end of the barrel? As in, the LMT factory barrels have a ring the gas tube passes through. I have a Craddock RTR 20” Service Rifle/SDM barrel I’m going to send off to them.

Thanks,
RIGREG

 

[matt33]

@matt33
How are the gas tubes on the D.Wilson conversions held in alignment, or fixed, at the receiver end of the barrel? As in, the LMT factory barrels have a ring the gas tube passes through. I have a Craddock RTR 20” Service Rifle/SDM barrel I’m going to send off to them.

Thanks,
RIGREG

There is no separate ring on the conversion barrels. It's just like a standard AR-15 barrel, the gas tube passes through into the upper like a regular ar. There does not seem to be any detriment to not having that ring near the barrel extension.

The only thing I'd like to modify is the depth of Mlok screws. The handguard is pretty narrow which I like, but M lok attachments need to be removed in order to detach and reset the barrel. I've read online that you can shorten these screws yourself to allow enough clearance so that you don't need to remove them prior to Barrel detach reset.

 

[RUTGERS95]

one load does not fit all...........

 

[matt33]

one load does not fit all...........

I'm aware of that, and 5 round groups definitely don't either. That's why I qualified the title as "unscientific". I only have so much time and ammo, but I wanted to share my general findings. I'm also positive I could have tightened things up with a Nightforce 32x rather than the Vortex 1-10.

I tested each one of these barrels fairly extensively over the past several months. Many 10 round groups were fired with 73 gr Bergers, 77 gr Bergers, 77 SMK's, AAC 77 gr, 69 SMK's, 60 gr VMax, 62 gr M855, and 55 gr IMI FMJ's.

I picked a handload that shoots as well in my AR's as anything I've tried, the 73 gr Berger OTM's with 23.3 grains of IMR 8208 in Starline 5.56 brass with a Fed GMM AR match primer seated at around 2.250" COL. I like this load because it's accurate, fast, and gives good ES/SD. It consistently performs better than any factory ammo I've tried.

The Bartlien barrel is by far the most accurate with all loads. Using 10 round groups at 100 yards with the Berger 73's, it's usually in the .6 - .9 MOA range. The Daniel Defense is usually between 1.1 and 1.4, The LMT SS 5R factory barrel is almost always over 1.5 MOA and the LMT chrome lined barrel is usually around or just over 2 MOA.

 

[Alpine 338]

I've had good luck with accuracy with my LMT rifles.

You show a picture a SS SPR 1/7 barrel, but mention a 16" 5R barrel.

I have several of the earlier (bright SS), and second generation (Black) that are LMT 18" SPR barrels, and they shoot exceptionally well, sub-moa. My first one with well over 3K rounds through it still shoots sub-moa, but as soon as it gets hot, the shots start to scatter beyond 500-yards. I primarily use various flavors of 77gr SMK factory ammo in either .223 or 5.56.

What amazed me my first LMT that I bought back around 2007, with 16" gas piston chrome lined barrel printed a 1-1/2" group at 300-yards using surplus Lithuanian SS109 ammo. That's the stuff that has the GGG head stamp, and runs Uber clean in an AR platform. Glad I stocked up on it when it was cheap and available.

 

[matt33]

I've had good luck with accuracy with my LMT rifles.

You show a picture a SS SPR 1/7 barrel, but mention a 16" 5R barrel.

I have several of the earlier (bright SS), and second generation (Black) that are LMT 18" SPR barrels, and they shoot exceptionally well, sub-moa. My first one with well over 3K rounds through it still shoots sub-moa, but as soon as it gets hot, the shots start to scatter beyond 500-yards. I primarily use various flavors of 77gr SMK factory ammo in either .223 or 5.56.

What amazed me my first LMT that I bought back around 2007, with 16" gas piston chrome lined barrel printed a 1-1/2" group at 300-yards using surplus Lithuanian SS109 ammo. That's the stuff that has the GGG head stamp, and runs Uber clean in an AR platform. Glad I stocked up on it when it was cheap and available.

LMT AR-15 Barrel 16'' 5.56 Stainless Steel 5R Cut 1:7" Twist https://share.google/wKMU22MIpubK8tXs0

I attached a link for the exact barrel I bought. LMT describes it as stainless steel, 5r cut rifled. It is 16" and stamped as shown in the photo. It has continued to show a little bit of improvement, but even the test tag that came with the barrel lists it as 1.51 MOA during test firing by LMT

I'm sure others have had better luck than me, maybe I just got a couple of duds. I have shot single five round groups with it as small as .6" at 100 yards, but it does not shoot that well consistently. It is consistently somewhere between 1.2 and 1.5 for five round groups at 100 yards

I think different people measure accuracy differently. I hear a lot of people say that their 5.56 LMT is "sub MOA all day," but I have yet to see a 10-round group with a factory 5.56 LMT that is less than 1 inch at 100 yards

I'm not saying it doesn't happen for people, I've just never seen it. If you're one of these people and you are reading this, please post some groups. Give me some details

 

[Alpine 338]

This is a 1/3 size IPSC target placed at 800 yards. 8 out of 10 shots on target with my first 18" LMT SS SPR barrel using factory Norma 223 with 77gr (I assume SMK?).

Four of the hits impacted in two spots on top of each other. My finger is on one in the top picture.

The rifle on top has a custom built Mk12 clone (not exact spec) upper put together by Ross Precision using a Bartlein SPR profile 4-groove SS barrel, with CLE chamber. Just going through the steps of breaking in the barrel, and zeroing the scope.

The upper receiver below that is the LMT MRP with 18" barrel that I used on the steel target above. I've used it at numerous team matches, including three Competition Dynamics Team Safari matches, where we placed second and forth the first two years shooting that match. I need to retire the barrel as I said previously it's starting to open up when it gets hot.

I prefer using a SB 4-16x42 with Gen 2 Mil Dot on my precision ARs. I feel it's the perfect scope fore that role. However, I do have a SB 3-20 on a CLE custom built upper that I have a Raptor LRF mounted above, which I typically use at another team event.

I shoot off a container in the Winter because I can get above the snow, and it's easy shoveling the snow off of that vs. clearing an area on the ground to shoot from.

 

[matt33]

8 out of 10 for any 5.56 at that distance is solid for sure.

I shoot mine quite a bit at 636 yards, which is the longest shot I can easily get on my property. This is about a 6.5" square on a 2/3 silhouette, using 5.56mm LMT with 16" Bartlein barrel from Craddock Precision. That low left shot was an overcorrection on my part, shooting was done with a Vortex 1-10 razor, more magnification would be great for days like that, but much of my shooting is closer