View Full Version : LMT 10.5" run with SAAMI spec ammo???
I have a new 10.5" LMT upper with LMT lower I SBR'd and the damned thing will not run with SAAMI ammo. Been tried with 2 different lower and several different proven mags, but the only thing it seems to run with 100% is M855. Tried Fed AE 55gr, Blackhills blue box 68 and 75gr, and Hornady NATO pressure TAP 75gr and NONE of them will run.
Is this normal for a new 10.5" LMT upper?
:(
I am going to go with no on this one. It should run with the ammo you mention. My 10.5 LMT runs on everything from Wolf, AE, Radway green, Malaysian, Federal, etc.
What happens with the "bad" ammo, FTF, FTE, etc?
Steve_Morrison
01-16-07, 18:57
Pretty tough to diagnose from afar without any pertinent information...
Perhaps you could let us in on the type of problems you are having- does your upper :
-fail to lock?
-fail to feed?
-fail to chamber?
-fail to extract
-fail to eject?
-Doublefeed?
-fail to cycle?
-shortstroke?
Whose bolt group are you using?
Who assembled the upper?
No, it is NOT normal. Our 10.5" LMT's run 100% with both SAAMI and NATO FMJ and OTM loadings from quality manufacturers (Black Hills, Federal, Hornady, Lake City, Winchester).
Robb Jensen
01-16-07, 20:13
I have a new 10.5" LMT upper with LMT lower I SBR'd and the damned thing will not run with SAAMI ammo. Been tried with 2 different lower and several different proven mags, but the only thing it seems to run with 100% is M855. Tried Fed AE 55gr, Blackhills blue box 68 and 75gr, and Hornady NATO pressure TAP 75gr and NONE of them will run.
Is this normal for a new 10.5" LMT upper?
:(
What bolt carrier, what buffer are you using? What types of failures are you having?
I recommend a standard Colt, FN, CMT or LMT M16 carrier, MP tested bolt, Crane O-ring or MGI D-Fender, H2 buffer and Brownells chrome silicone standard power buffer spring. Also use good mags like C-Products, USGI mags with Magpul followers or HK mags.
My 10.3" LMT short barreled rifle has a CMT bolt, Colt M16 carrier, Wolff XP M4 extractor spring w/Crane O-ring, ISMI buffer spring and CMT H3 buffer and it'll run even on American Eagle 55gr .223 and weak Wolf 55gr .223 This barrel was a 14.5" LMT factory barrel that I had cut down to 10.3" and the gas port opened up by Randall Rausch at www.ar15barrels.com I also used my Ned Christiansen 5.56mm neck and throat chamber reamer on it which barely removed anything.
If you want to send me the entire upper and I'll see if I can make it work. (no charge other than return shipping).
Specifics:
CMT M16 bolt/carrier group with G&R's Crane O-ring, LMT lower with LMT SOPMOD stock & receiver extension, ISMI buffer spring, H2 buffer, CMT std trigger group... All is brand-spankin new.
Symptoms are that it goes bang, and will usually extract/eject but not cycle a new round off the mag other than ocassionally with Hornady TAP. Out of approx 60 rds Fed AE 55gr, 20 rds Hornandy NATO spec 75gr TAP, and 20+ rds each of Black Hills blue box 75gr and 68gr, it cycled one round into the chamber after firing a total of maybe 10 times. NEVER cycled more than once after going bang. Load one rd into the mag and it will NOT lock open on the empty mag.
Used 3-4 different mags that work fine in two other AR's - LaBelles with magpul followers, and CProducts...
Acts like it is not getting enough gas to me, but I sent it back to the builder and he said it seems to work fine on the builder's LMT lower using M855... but not with Black Hills SAAMI spec. LMT says they won't warrant it for anything other than NATO (M855 or Mk262 I assume) ammo.
I've been advised to try swapping out the ISMI spring with the stock stainless spring that came in the upper, then if that doesn't work, swap the H2 for an H buffer. I'll advise when/if we get it sorted out.
The big surprise to me is that the red box TAP wouldn't cycle it. that's pretty hot stuff.
Robb Jensen
01-16-07, 20:32
Try a standard CAR length buffer spring along with the H2 buffer. If you need on let me know I have one I can send you. If it doesn't work with that then it should go back to LMT.
gotm4,
Thanks for the offer(s)! I will see what happens. Hopefully it's a combination of factors and not that the upper is some kind of lemon. The new ISMI spring is noticeably harder to cycle by hand than another one I have in another lower that has maybe 500 rds shot with it. I do have the stainless spring that came in the lower from LMT I can try. It's about 1.5-2 inches shorter than a new unused ISMI spring I have lying on the bench right next to it, so hopefully that will make it work.
I had the same problem, change back to the original spring and it should work fine.
I built this weapon and have it now. The weapon runs like a top with M855, H3 buffer and ISMI spring. The lower is mine and is how I run my 10.5 as well. When I switch to weaker ammo, the bolt will not lock back, but does cycle.
Just as an FYI to those that are unaware of this, if you buy a LMT 10.5 upper and it doesn't run with the ammo you like and you send it back to them to fix and they get it to run with mil-spec ball, they will send it back and advise you that it runs fine. Their opinion is that they build their guns to run mil-spec ammo and if it doesn't, then that is on the end user.
C4
I don't hold it against you Grant! I've bought enough other stuff from you to know it's gotta be "just one of those things".
Let me know what happens when you try a std carbine spring and/or lighter buffer with the A2. I may still have to tinker with changing different variables after I get it back from you, but at least I'll know where to start.
When I first got my 10.5 LMT last month it did the same thing as you described. Turns out the bolt was out of spec. The bolt was dragging really bad on the top round in the magazine, causing the spent case to extract, and eject, but not feed a new round. A lil work with a lode stone, and all is well.
Dumb Question, but what ammo is and isn't MIL SPEC ? I plan in the future to get a LMT 10.5 Upper,LMT FA boltcarrier group to go on my LMT lower.
UPDATE: Grant (G&R Tactical for those of you who've been asleep) said he's going to start from scratch and send me a new LMT upper.
Now that is above and beyond the call of duty, considering LMT doesn't sound too interested in fixing this upper.
THANK YOU GRANT!!!
Dumb Question, but what ammo is and isn't MIL SPEC ? I plan in the future to get a LMT 10.5 Upper,LMT FA boltcarrier group to go on my LMT lower.
Anything with a Military designator (M855, MK262, M193, etc).
When I build a LMT 10.5, I test fire it with M855 (which is all I shoot). The issue is that sometimes the uppers will not run with anything BUT mil-spec ammo and most customers don't shoot it.
C4
UPDATE: Grant (G&R Tactical for those of you who've been asleep) said he's going to start from scratch and send me a new LMT upper.
Now that is above and beyond the call of duty, considering LMT doesn't sound too interested in fixing this upper.
THANK YOU GRANT!!!
Your welcome.
C4
...When I build a LMT 10.5...
C4
Grant,
I'm curious what constitutes "building" a LMT 10.5. Aren't these complete uppers?
Grant,
I'm curious what constitutes "building" a LMT 10.5. Aren't these complete uppers?
I took it all apart and put it back together. :D
I installed a LT 7.0 rail and a KX3.
C4
docsprague
01-30-07, 23:49
I just got a LMT 10.5 as well. First time out it would only run on 5.56 pressure ammo( Lake City and WCC m193 and Hornady 5.56 Tap). And it occasionally had problems with it until I took out the H2 buffer. It would not run on the PMP 223 I had. Took it home clean and lube the bolt again. Took it out the next day and fired 20 rounds of 223AE and 20 rounds 223 S&B through it and both worked fine. I plan on putting the H2 back in and giving it a try as soon as we get warmer weather here in MO.
To the pros: How much of this problem could be just getting the gun broke in?
Either I got lucky or I got a good one. Although I have a standard spring, the buffer is a 9mm and m16 carrier group. Runs 100% with everything shot so far, 55 BH sp, 55 gr fed 193 and AE 77 bh 855
I just got a LMT 10.5 as well. First time out it would only run on 5.56 pressure ammo( Lake City and WCC m193 and Hornady 5.56 Tap). And it occasionally had problems with it until I took out the H2 buffer. It would not run on the PMP 223 I had. Took it home clean and lube the bolt again. Took it out the next day and fired 20 rounds of 223AE and 20 rounds 223 S&B through it and both worked fine. I plan on putting the H2 back in and giving it a try as soon as we get warmer weather here in MO.
To the pros: How much of this problem could be just getting the gun broke in?
10.5's are difficult AR's to get to run well with all ammo types. AR's typically are not broken in till around 500rds so give it a little time.
C4
Per conversation with Karl Lewis, the 10.5" CQBR uppers are designed to use the standard carbine or "H" buffer.
At one time most of SOCOM's M4's used the standard carbine buffer. The Navy had the M4a1 with full auto and the "H" buffer(vs m4 with burst and standard buffer). So the CQBR was designed to work with the majority of SOCOM weapons.
Be advised M4A1's(14.5" barrel), in extreme cold, will sometimes show difficulties with a "H2" buffer.
Per conversation with Karl Lewis, the 10.5" CQBR uppers are designed to use the standard carbine or "H" buffer.
At one time most of SOCOM's M4's used the standard carbine buffer. The Navy had the M4a1 with full auto and the "H" buffer(vs m4 with burst and standard buffer). So the CQBR was designed to work with the majority of SOCOM weapons.
Be advised M4A1's(14.5" barrel), in extreme cold, will sometimes show difficulties with a "H2" buffer.
Have heard the same thing from LMT. This is why I find it so interesting that Colt ship's their 11.5's with standard Car buffers.
C4
I change my buffer to heavier weights as the gas port erodes & the cyclic rate goes up. Whe using specialty ammo, esp some frange types, the port erodes so fast one will experience "bolt bounce"malfunctions on auto. Diagnostic reveals the hammer forward on a live rd.
Some frickin' UPS employee absconded with my replacement LMT upper, so I'm back to square one... waiting on upper number 3, for crying out loud. Simply amazing how much of a pain in the arse this SBR has turned out to be. :mad:
Grant's taking care of things, though and I will (hopefully) end up with something better than I started out to get anyway.
ashooter, How is that gas piston AR of yours running?
My LMT 10.5" runs no matter what I feed it. Wolf, PMC, UMC, WWB, and XM193.
My current configuration is:
LMT 10.5" upper
LMT lower
H2 Buffer
Standard buffer spring
LMT BCG with Colt HD extractor spring and O-ring
Noveske KX3
Robb Jensen
02-01-07, 10:58
My LMT 10.5" runs no matter what I feed it. Wolf, PMC, UMC, WWB, and XM193.
My current configuration is:
LMT 10.5" upper
LMT lower
H2 Buffer
Standard buffer spring
LMT BCG with Colt HD extractor spring and O-ring
Noveske KX3
LMTs typiclaly run very well usually anyway but the KX3 helps even borderline guns a lot. I'm planning on building a 10.5" 6.5 Grendel w/VLTOR MUR upper rec., DD 7.0" Lite rail, 'FN' contracted carrier and a PRI gas buster. If there's a KX3 that will fit I want to get one. Otherwise I may run my .30 cal AAC Cyclone suppressor if it's possible to get the bbl in 5/8x24 or get an adapter for it.
My LMT 10.5" runs no matter what I feed it. Wolf, PMC, UMC, WWB, and XM193.
I would have to agree as mine also runs like a Swiss watch no matter what I feed it. I have not tried any Wolf yet though.
My current set-up:
LMT 10.5" Upper
LMT BCG w/ CRANE o-ring, Wolf HD extractor spring, and black insert
ISMI buffer spring
LMT H2 buffer
As a matter of fact mine has only had one single failure of any kind (5,000 rounds and rising) and that was ammo related (blown primer).
LMTs typiclaly run very well usually anyway but the KX3 helps even borderline guns a lot.
I should have been more clear in my post. All that ammo was tested BEFORE I installed the KX3. Back when I first broker my 10.5" I just had the standard A2 flash hider on it. In fact, I haven't even shot my LMT 10.5" since I installed the KX3.
I've had one problem with mine that could have been avoided if I did a little PM. A simple swapping out the old "crane-kit" for a new one fixed the problem. I have a little over 5K through my current upper (on my 2nd one) and it's ran great with M855, M193 and AE 55gr. No Wolf.
My set-up:
LMT 10.5" upper
LMT F/A BCG w/ Crane-Kit
USGI spring
H-Buffer
Some frickin' UPS employee absconded with my replacement LMT upper, so I'm back to square one... waiting on upper number 3, for crying out loud. Simply amazing how much of a pain in the arse this SBR has turned out to be. :mad:
Grant's taking care of things, though and I will (hopefully) end up with something better than I started out to get anyway.
Hmm, wonder how they did that? Trust me with an item that large it is getting extremely hard to do.
Hmm, wonder how they did that? Trust me with an item that large it is getting extremely hard to do.
Apparently not, and trust me I know. :mad:
I’ve had packages lost by both UPS & FedEx.
ashooter, How is that gas piston AR of yours running?
hehehe.... smartass.
Actually Dinger, I have "seen the light" and am munching a mouthful of crow as I type this. No more pistons for me unless they are in a system that was designed from the ground up. Masada perhaps?
BTW - Pat Rogers is a good teacher. ;)
Hmm, wonder how they did that? Trust me with an item that large it is getting extremely hard to do.
Here's a quote from the tracking page on UPS' webiste:
"MERCHANDISE IS MISSING. UPS WILL NOTIFY THE SENDER WITH ADDITIONAL DETAILS.;ALL MERCHANDISE MISSING, EMPTY CARTON WAS DISCARDED. UPS WILL NOTIFY THE SENDER WITH DETAILS OF THE DAMAGE"
Sound like somebody walked off with it to me.
hehehe.... smartass.
Actually Dinger, I have "seen the light" and am munching a mouthful of crow as I type this. No more pistons for me unless they are in a system that was designed from the ground up. Masada perhaps?
BTW - Pat Rogers is a good teacher. ;)
Crow, I know what that taste like :o
See my signature lines.
:D
ic_guerrero
02-27-07, 15:14
My LMT has been running with all types of ammo as well, but will only lock the bolt back occasionally with Mk 262. I'm currently running a carbine buffer w/ a standard carbine spring.
My LMT has been running with all types of ammo as well, but will only lock the bolt back occasionally with Mk 262. I'm currently running a carbine buffer w/ a standard carbine spring.
Have you run M855 or XM193 in it? Results?
C4
ic_guerrero
02-27-07, 15:29
Have you run M855 or XM193 in it? Results?
C4
Not yet. I drove around for three hours yesterday looking for any load in 556 and came up empty handed. The Mk 262 did it lock it back a few times, I just can't remember if it was the first mag or the last mag that didn't do it.
LMT is indeed made for milspec powered loads, their gas port is just the right size & it works.
BM has a much larger port on their shorties to accommodate the civ/le crowd & their dubious ammo purchases. I've had several BM 11.5" upper so overgassed they wouldn't function on auto... bolt bounce issues. More recoil & run really dirty too
Bravo Co upper also have a larger gas port to accomodate the questionable ammo most civi & PDs run through their guns. The one Bco 11.5" I have runs fine on auto, however.
LMT is indeed made for milspec powered loads, their gas port is just the right size & it works.
BM has a much larger port on their shorties to accommodate the civ/le crowd & their dubious ammo purchases. I've had several BM 11.5" upper so overgassed they wouldn't function on auto... bolt bounce issues. More recoil & run really dirty too
Bravo Co upper also have a larger gas port to accomodate the questionable ammo most civi & PDs run through their guns. The one Bco 11.5" I have runs fine on auto, however.
True and most folks don't seem to shoot mil-spec ball (which is why we see problems).
C4
ic_guerrero
03-03-07, 20:05
Have you run M855 or XM193 in it? Results?
C4
Grant,
I went out to the range w/ some XM193 and it locked the bolt back every time. It ran like a champ using mil spec ammo. Once again this was using a standard spring and a carbine buffer.
Marco
PALADIN-hgwt
03-03-07, 20:37
xxxxx
Grant,
I went out to the range w/ some XM193 and it locked the bolt back every time. It ran like a champ using mil spec ammo. Once again this was using a standard spring and a carbine buffer.
Marco
Yes it should. If it didn't, there would be something VERY wrong with it.
C4
Peacekeeper1408
03-24-07, 02:59
I've been trying to find the LMT port size for a 10.5", but can't find it anywhere.
CarlosDJackal
03-30-07, 20:26
I use an LMT upper on my SBR and I shoot nothing but 55-grain .223 Remington "commercial" ammo without a hitch of any kind. FWIW.
docsprague
05-03-07, 23:25
Does anyone know if LMT uses the same size gas port holes on their 10.5 MRP barrels? I have never heard of them having the same issues that some of the standard 10.5 have.
Edit: I dont know about the LMT MRP barrels but a standard LMT 10.5 is a .070 gas port. I just had mine opened up to .076 to get it to work properly.
Robb Jensen
05-04-07, 04:12
Does anyone know if LMT uses the same size gas port holes on their 10.5 MRP barrels? I have never heard of them having the same issues that some of the standard 10.5 have.
The MRP 10.5" barrels and the regular LMT 10.5" barrels both use carbine length gas systems so there's a very high probability that the gas ports are the same. If you really want to know I would call LMT to verify.
I use an LMT upper on my SBR and I shoot nothing but 55-grain .223 Remington "commercial" ammo without a hitch of any kind. FWIW.
Same here... Wally World Rem UMC, only when I run out of XM193...
CarlosDJackal
05-05-07, 22:52
Same here... Wally World Rem UMC, only when I run out of XM193...
I finally took a look at my shooting log and I have also shot the following rounds: S&B 55-grain FMJ, GA 55-grain FMJ "Heat", Hornady 55-grain TAP, Hornady 60-grain TAP, and Hornady 75-grain TAP. No issues on any of them.
I heard recently that LMT opened up the port a bit on the 10.5's to get them to function with a wider variety of ammunition. Is there any truth to this?
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