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

matt33

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Minuteman
Apr 1, 2009
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Bradford/Susquehanna Co, PA
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
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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.
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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)
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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.

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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

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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:
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@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.
 
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@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
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.
 
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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.