LMT 10.5" Range Report w/ Chrony Results

General Firearms NFA
1

Took the the 10.5" LMT out for her maiden Voyage this morning.

Aimpoint Micro H-1
Trop rear BUIS
H2 Buffer
Denny’s (GTS) Super Duty AR15 BCG

Temp: 79 (when I got there) - 85 (when I left)
Wind: Nill :smiley:
Range: 50 yds. (Just sighting er’ in)

of rounds fired: 135 (not that big of a day)

Chrony: 10 Feet from Muzzle
NO malfunctions. All Bras was ejected about 3 feet behind and 7-10 feet to the right.

Win. 5.56 Q3131 55gr.
90 rounds fired:
Hi Vel: 2959
Low Vel: 2749
Average Vel: 2840
No malfunctions. Decent Accuracy. 1.5" at 50 yds. Hey, I’m no marksman…yet. The first two five round strings the bolt would not lock back on the last round. After it seemed to break in, the bolt would lock back on the last round. Slowfire for accuracy and Chrony results. Shot one six round rapid fire…no malfunctions and lthe bolt ocked back on last round. Sharp recoil (for a 5.56)

Black Hills 75 Gr. Match HP
25 rounds fired:
Hi Vel: 2405
Low Vel: 2322
Avg Vel: 2362
No malfunctions. Excellent Accuracy. One little ragged hole of about .5-.75 at 50 yds. Always locked back on the last round. Good stuff.

PMC 55 Gr. FMJBT
20 rounds fired (one box)
Hi Vel: 2554
Low Vel: 2426
Avg Vel: 2514
No Malfunctions, but would not lock back on the last round. Not a surprise. I chrony’d this stuff through a 16" a while back and it was about 2850. Grouped well, though. About 1.5" at 50 yds (all 20 rounds).

I’m thinking that as the gun “breaks in” it will lock back the bolt on the last round consistently. If it doesn’t I might consider switching to an H buffer (as opposed to my current H2). Anyway, I was pretty happy with it, and with the preformance of the Q3131. I was surprised that the POI was not that different at 50 yds. Yes, it’s only 50 yds., and looking at the three it’s easy to see that the POI is different, but not that different. The Q3131 is dead center, the PMC is about and inch above, and the BH and inch above (the Q3131) and 1/2" to the left. Obviously, more distance will really open up the differences in POI. I look forward to more shootin’ with this one. :D:D:D:D:D:D

2

It shouldn’t require “breaking in”. Move to the lighter buffer.

My LMT 10.5 has been flawless with just a regular carbine buffer. I don’t understand everyone newfound fixation with H2 buffers…

3

Nice!! The 10.5" is my favorite AR bbl length!

Seems like pretty good results from the 75 grain Black Hiolls!! Does the H-1 have a 2moa dot or 4moa?? I have not tried a dot sight yet, but I might need one!

Thanks for the report!

Jon

4

This thread is useless without pics… :stuck_out_tongue:

5

The H-1 has a 4 MOA, although most folks tell me that it is actually about 3.5 or so.

Not the best pic, but here she is. I’ll try to get better ones up soon. BTW, I switched around my ADM mount so that the lever is now on the left side:

If I change to the H Buffer (down from H2) will that change anything in terms of POI?

Also, any rule of thumb for cleaning? Since I only shot 135 rounds I just popped er’ in the safe and figured I’d wait till 300 rounds or so for a proper cleaning. Do ARs need to be cleaned everytime you shoot.

6

As far as changing POI, I’d say not much (if any), but it’d be best to act like it does anyway.

As far as cleaning, most folks will tell you that if you rely on it in any capacity it’s best to clean it any time it’s but I’ve gotten real lazy lately and my definition of “dirty” has changed a little.

I’ve also come to believe that a rifle will run dirty perfectly well, but it won’t run dry. So every time I’ve come home from the range I’ve just re-oiled it a little, cycled it a few times & put it away. I figure in another six months or a thousand rounds I’ll clean it good & start again.

ETA: How cute, you put bubble wrap under your rifle so it wouldn’t get marred up by the floor. Start going to some matches and you’ll get over that real quick.

7

Maybe he’s protecting the floor… :wink:

PS. Nice no-nonsense looking build you have there.

8

I’m in the process of putting together an identical setup as the original poster - great minds think alike - and my understanding is that LMT sends these guns with a regular carbine buffer (not a H or H2).

I’m scratching my head and wondering why I would need a H or H2 for a semiauto gun. Cyclic rate is not an issue. I suppose there is some argument that a H buffer and the slightly heavier full auto bolt carrier would create more positive seating of the bolt as it travels forward to reload the chamber, but other than that I can’t think of a reason to run a heavier buffer on a semiauto gun.

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Nice picture. Are those Hanes socks? LOL Funny stuff! I like the gun though, good stuff.

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Actually, yes. They are Hanes, and they did not require a Tax Stamp. However, the rifle did:D.

BTW: The bubble wrap is to protect the floor. I don’t want to have to tell my wife it was me who scratched the tile (she’d figure it out anyway!:D).

If the H2 Buffer is a problem waiting to happen (eventhough I had no malfunctions and just issues with the bolt locking back…sometimes), then I’ll just switch it out to the standard H Buffer.

11

You won’t even come close to scratching that tile with an aluminum receiver bro. We drop hammers on tile all the time, usually without a single mark left behind. You couldn’t scratch that tile by lying a gun down on the floor if you wanted to…

12

Something I found out about the PMC “Bronze” stuff. It doesn’t like SBRs because of the slow-burning powder they use. Both my LWRC and LMT 10.5-inch uppers ended up getting so dirty with the PMC ammo (unburnt powder). So much so that it looks like someone dropped a handful of sand into the receiver. I actually got a lot of malfunctions with that ammo and none since I stopped using it.

Were those Black Hills 75-grain Match rounds from a “blue box” or a “red box”? Thanks for sharing!! :slight_smile:

13

Thanks for the info Carlos. One thing I took a look at after reading a post by demigod. I bulit the lower w/ an Armalite parts kit. BTW: its trigger is a bit on the rough side, especially after shooting my 556. Anyway, like demigod, I took a look at the bolt release/catch and found that it was flimsy, easily moved/woblled back and forth, and didn’t feel like it had a lot of spring tension. So, I replaced the spring, roll pin, and catch/release (STAG Arms). I made sure that the roll pin was in correctly. There is a lot more spring tension and no wobble.

This may not be the issue, but I want the right part working nice and tight like it should. I’ll try the H2 again, and then the H if I have any issues. As you can see from the pic, I do have the KNS anti-rotation pins. Couls that be causing an issue?

14

I think you went the opposite direction. I cut my spring to reduce the spring tension. My oldest and most reliable guns (one of which is a factory Colt LE carbean) have very light spring tension and the bolt catch has a reasonable amount of float/play in it. This ensures that the mag spring doesn’t have to fight the bolt catch group to get the bolt to lock back.

15

I’m not sure what the burn rate of the PMC powder is. But PMC bronze won’t run worth a shit in rifle gas systems. GotM4 pointed this out. So I went out and tried some in my rifle. I had the same results… short strokes… weak cycling, etc.

16

Thanks for the explanation. The new bolt catch/release that I put in works like any other AR I’ve had/seen. It doesn’t stick, but the tension is as it should be. Again, this might not be a source of any issues tight or loose, but I want it to be right.

The PMC acutally cycled my LMT fine, but I only shot 20 rounds. It just wouldn’t hold the bolt open on the last round. But I can see by it’s low velocity performance that it could cause issues. Definately noticeably softer than the 5.56 ammo.

Thanks again for the info.

17

That PMC is .223 ammo. For 55 grain, this upper needs NATO pressure ammo to be reliable (unless you want to change the buffer and set it up for SAAMI ammo).

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UPDATE 11/1/08

Took her out today and shot 250 rds. No FTF or FTE. All shots at 50 yds. But Win Q3131 still did not always lock back on the last round with an H2 or H buffer. Red Box BH 75 dr. Match had same issue w/ H Buffer only.

First, I shot more Q3131. I took three mags, loaded them w/ 2 rounds each and shot em. two of the three did not lock back on the last round. I tried this three more times with the same result. So I switched to the H Buffer. Noticeably more recoil and “Sproing,” but still had failures to lock back on the last round. But NO FTEs or FTFs. I shot a 30 rd. magazine and 10 rnds rapid fire, and both times the bolt locked back on the last round. I was using the H Buffer during this drill. Avg vel. was 2859

Shot twenty rounds of American Eagle 55 gr. FMJBT(5 rds. at a time, only had one box of 20). Decent accuracy, always locked back on the last rnd, using H Buffer. Did not use the H2 with this ammo. Avg vel: 2633 Odd, lighter ammo but always locked the BCG back on the last round. ???

Shot 100 rounds of Prvi Partizan 55 Gr. M193. This ammo was awesome. Excellent Accuracy. Even better than the Q3131, and not far off from the BH Match ammo. Remember, I was only shooting at 50 yds. I did rapid fire with 20 rds and 10 rds. Again, this ammo locked back on the last round consistently w/ H Buffer. Did not use the H2 with this ammo. Didn’t use the H2 on this ammo… Avg vel: 2749. Again, softer ammo, but consistent lock back on last rnd. ???

Lastly , shot the last 25 rounds of the Red Box Black Hills 75 Gr. ammo. Shot 5 rnds at a time. Did rapid fire w/ 5 rnds. Accuracy was excellent. I used the HBuffer only with this ammo. The recoil was noticeably sharper with the H Buffer than it was last week when I shot it with the H2 Buffer. No FTEs or FTFs, but this time I got several failures to lock back on the last round. Incedently, the rapid fire locked back on the last round. Avg. vel. 2380. More recoil, but problems locking back on the last round. ???

Well, I’m still lovin’ the LMT 10.5". It’s a blast. Whether using the H or H2 buffer I have not experienced any FTEs or FTFs. Just failure of the BCG to lock back on the last round with Q3131 with both the H & H2 and with the H on the BH 75 gr. Match. I checked my bolt catch/release. It seems normal to me, not sticky. I tested compared to other ARs and it seems normal.

I thought maybe that the H2 was to heavy for the Q3131 and that was the issue, but it did it also with the H buffer. I thought that it was weird that the BH always locked back w/ the H2 but not the H. Maybe I need a heavier buffer for these rather than a lighter one? Just a thought. Suggestions ?
Next time I’m going to teste the Prvi M193 w/ the H2 buffer. I like how the rifle shoots with the H Buffer. Very smoothe, and noticeably less vibration and yes, even recoil.

19

IMO:

  • Lube the weapon heavily
  • Use only USGI, HK, or P-Mags
  • Use only Mil-Spec ammo.

I would bet just lubing the weapon will fix all issues. I’ve owned two LMT 10.5’s and both ran like a champ when properly lubricated, and using high quality mags & NATO spec ammo.

I also had luck with H2 buffers.

20

UPDATE 11/2

Put in the carbine buffer and it ran flawlessly with all ammo and locked back every time, Q3131 included. You’ll be seeing an H2 buffer upr for sale soon! Thanks everyone for your input and help!!