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Posted: 5/16/2004 9:17:13 AM EDT
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I just completed a custom .223 upper for a customer, utilizing (at the customers request) an LMT enhanced bolt. This was my first experience with this bolt in .223. It will not extract. The upper cycles perfectly when the LMT bolt is replaced with a Colt , RRA, or DPMS supplied standard bolt. I inspected the extractor and bolt thoroughly, and found nothing obviously wrong. In comparison, I noticed some differences between the LMT and other bolts. For example, using precision guage pins, there is .274" between the ejector and extractor on the LMT, as compared to .262" on a new RRA bolt, and .265" on a used Colt bolt. I'm about to set up a precision electronic depth guage to measure the depth of the groove in the extractor itself, but haven't done so yet. Has anyone else had a problem? |
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Correct. We took one of the springs out of a new bolt and immediately had extraction failures. The twin spring arrangement provides the same pressure as the standard spring, with one missing or broken you only have half the spring force and it becomes uneven. That said, we've seen 30,000 rounds on these bolts before extractor spring failure. HFG |
Right. One spring pushing from one side would have problems. Two springs should last longer than the one spring on a standard bolt head. Just would be nice if one could break and it still function. What parts are interchangable with standard bolt parts on your bolt head? Even pins count as standard parts. |
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Both springs are the same length On further examination, with a 30X microscope and a digital electronic depth guage, it appears that a couple of machining processes may have been left out. The recess in the bolt, where the extractor seats, is slightly higher than the diameter of the face of the bolt, thereby keeping the extractor from traveling inward toward the center as far as it should. All of the other bolts I have in the shop, including the LMT bolt for the L-W .499, have this surface recessed below the diameter of the face. Additionally, the 'hook' of the extractor itself appears to be angled the wrong way, allowing it to slip off the already inadequate grip on the rim of the cartridge. If I can figure out how to take pics through the microscope, I'll post them. |
QA issue then. LMT need to tighten up on this if they are going to do well in the commercial market, seems they pick and choose which products get full QA and which get cursory.
The only standard parts are the pins, gas rings and ejector. HFG |
Here is a pic of the upper in question (during testing), along with another ongoing project. It's a Colt large hole flattop receiver, with a 14.5" Colt 1/7 barrel with permanently attached KAC M4QD comp, wearing a KAC MRE RAS, flip-up front sight/gas block, JP Enterprises stainless carrier and (now) a Colt bolt. |
Springs aren't I guess. Oh well. |
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We have the same experience when we tested the Enhanced bolt of LMT. The springs are weak. we test fired it full-auto and it had a failure to extract. we also found out that there is no advantage of the LMT bolt carrier assembly compared to the standard M16 bolt carrier. |
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The theory behind the enhanced carrier is that it delays the opening of the breach allowing the gas pressure to reduce more and gives more consistant ejection and better timing. We have used both and find no advantage to the LMT enhanced carrier. We also had an early LW.499 with the enhanced carrier which was not reliable. Apparently, LW engineers spent a lot of time argueing with LMT against using the enhanced carrier in the .499. As soon as they swapped it for the standard carrier, the gun worked fine. Seems the gas delay to the lower pressure .499 caused by the enhanced carrier led to a negative gas pressure in the system and the bolt group short-stroking. So there you have it. The enhanced carrier does slow down the opening of the breach - does it have any effect in the real world of 5.56mm? - not really. HFG |
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THE THREADED PORTION OF THE BARREL IS 0.620". SUBTRACT THAT FROM 14.5". ADD THE LENGTH OF THE KAC M4 QD COMP, 1.875". IF SHIMMED CORRECTLY WITH THE KAC SHIM KIT, NEVER MORE THAN APPROX. 0.070", YOU'LL NEVER MAKE 16". PLEASE DO NOT MAKE FOLKS THINK THIS WOULD GIVE THEM A 16" LEGAL BARREL. IT WILL NOT. WES |
Are you calling me a liar? |
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Lets stay on track with this thread- barrel lengths can go on another thread. SMGLee got a LMT bolt or bolt and carrier a looong time ago and I remember he had some initial problems with function- IIRC he was going to try different ammo/ carrier / bolt combinations to see what effect that had on reliability- He may have something to add to this discussion.. |
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I would think it was to do with a 5.56mm LMT enhanced bolt failing to extract. Just what that has to do with LMT/LWRC is beyond me? As I said above, we have seen these springs go to 30,000 rds, the bolt material is good. As for the lug design, from our perspective it just means that if they are going to let go, they do so in a benign way. HFG There are other threads on this failure to extract problem all relating to 5.56mm. |
Just like in the skydiving industry. When your life depends on your gear, never buy anything "new". Always wait till its been around the real world for a couple years at least. Let other people beta test for you. |
I've seen Colt, RRA, Smith Ind., Armalite, Bushmaster and all manner of other bolts also fail to extract. Is this news? I think it's funny that this bolt design, not very long ago, was being touted as the savior of the Leitner-Wise 499 project....now suddenly it's crap, out-of-spec junk. Gosh, I know of several threads where we 458 SOCOM users were told that our Colt, modified bolts, were inferior to the LMT designed Leitner-Wise bolt. How soon we forget.......now that LMT and Leitner-Wise are on the outs, we start hearing the "REAL" story.......hmm....... |
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I don't think that is the point of this thread at all. Bandit was asking if anyone else had this problem, some have, some haven't and as one of the main features of this bolt is the fact that it addresses the extractor spring failure of the standard bolt system, when this stops working it's perfectly legitimate to ask why. I don't see anybody here saying it's "crap, out-of-spec junk". It's a good bolt, by and large well made and a useful addition to the system. HFG |
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Forgive me if I am wrong, but I thought HipFiredGun was Karl Lewis, head guy at LMT? If so why is he downing the product? So the LMT "enhanced carrier" isn't any better than the RRA "enhanced" carrier that I have right now? Even for the 14.5" barrel it is supposed to be for? So is there even an advantage to having two non-standard springs on a non-standard extractor if it won't even work with one spring broken? And some people are saying that it won't even work for very long with BOTH springs? The way everyone is talking, I am starting to think no. I was planning on getting this bolt group for the 14.5" barreled upper I was going to build up in the future, I guess now maybe I won't. |
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The bolt is good so go with it if you want. It is unlikely that you will ever need any extractor springs. Regarding the enhanced carrier, that's down to you but if it were me I would save the money and buy standard, that's what we did. All LMT stuff is good, you just have to make sure you get it on a good day when the QA guy's have been doing their job LOL! HFG |
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It's all about performance. The LMT bolt is a good addition and will improve the operation and reliability of the rifle. We are looking at some alternatives now that go beyond the LMT bolt and its design and take the weapons reliability to the next level - are these needed for civilian use? It's the same question as why have a car that goes faster than the speed limit? HFG |
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THERE'S NO REASON TO THINK YOU'RE BEING DISPARRAGED, JOHN, BECAUSE I QUESTION SOMETHING. TRY TO REMAIN OBJECTIVE. I'M TRYING TO KEEP FOLKS FROM GETTING THE IMPRESSION A KAC M4 QD COMP WILL MAKE 16" ON A 14.5" BARREL, BECAUSE IT WON'T IF PROPERLY INSTALLED, NOT WITHOUT A SPACER OF SOME SORT. IF SOMEONE WELDS ONE ONTO THEIR 14.5" WITHOUT SUCH A SPACER AND IT COMES OUT LESS THAN 16", THEY HAVE AN ILLEGAL BARREL LENGTH THEY CAN'T READILY CORRECT. PLEASE EXPLAIN WHAT SORT OF CRUSH WASHER OR SHIM ARRANGEMENT YOU'RE USING TO DO ACHIEVE 16.1". KEEP IN MIND THE KAC M4 QD COMP IS DESIGNED TO BE INSTALLED ONLY WITH THE INCLUDED KAC SHIM KIT. WES |
I dont think this circumstance with this particular LMT Bolt makes all of them "pieces of Junk" I have heard nothing but great things about the Enhanced Bolt.I bought one and mine works flawlessly so far.But then again so have all of my Colt bolts as well.What Im traying to say i guess is that there are going to be some issues with every companies gear sooner or later.Certain items will make it to the customer that shouldnt of.But that does make all of them bad. my .02 |
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I have several enhanced bolt on standard carrier and one enhanced bolt assembly in a SPR. I had one problem at the beginning and one later. All can be traced to something other then the carrier. the first problem was the upper had a non M4 feed ramp barrel installed to a LMT feed ramped upper. the ledge on the barrel was causing double feeding. the second problem was I tried to use the LMT enhanced carrier assembly with PRI fatboy and Colt 9mm buffer. once I switch out the parts, the gun worked flawlessly again. |
Ok, SMGLee, I can see how those situations were caused bye other components. So, ok, I am still undecided. How much is a spare extractor/spring pack going to cost me if I decided to get one of these bolt heads? Does the coating have any benefit? I know that it is supposed to be slicker, but how much can that be improved on compared to a standard bolt head? |
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It would seem the enhanced carrier was designed to reduce the shock thet short gas system weapons experience and that the enhanced bolt was designed to extend extractor spring life and eliminate the problem of bolt and lug breakage in in short gas system M-4 type weapons. I can see where the enhanced bolt would be a good item in all lengths but the enhanced carrier only would seem to make sense in weapons with a short gas system. |
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TWO SPRINGS AND EXTRACTOR FOR LMT ENHANCED BOLT, $35. WES GRANT MSTN.BIZ |
Ok, that isn't too unreal. |
I didn't think so the first time you questioned. The second...?
All other issues aside for the moment (and there are some which we will have to resolve privately), my method of attachment is, to me, a trade secret. Let it suffice to say that the upper receiver in question meets all legal requirements, and the method of attachment has been engineered to be at least as strong as full thread engagement. Being in daily contact with some of the best minds in the firearms industry does have its advantages. That said, it's not rocket science. I'm sure you'll figure it out if you try. |
I think someone (HFG) said the springs worked for around 30,000 rounds. that is pretty long to me. |
So If I get one of your uppers with this set up, and then have baffle strikes and ruin my KAC Can would you replace the can? |
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It is by now pretty well documented that during cycling of a normal M16 bolt, there is a period where the extractor of the M4 lifts off the rim of the case and the case is held to the face of the bolt by gas pressure. After the initial rearward movement, the extractor settles back down over the case rim again. If the LMT bolt suffers from the same phenomenon (extractor lift) then the enhancements designed to improve functioning in short gas systems (or higher pressure gas systems like suppressed full-autos) work by delaying the gas pulse until the pressure is lower (pigtails, Fatboy gas tubes, LMT carrier with 3-holes for gas, etc.). If you use these same enhancements in a semi-auto operating under far less pressures, you may be enhancing your way into a malfunction when there is no longer enough gas pressure to hold the empty case to the bolt face during extractor lift. |
Not a chance. For one thing, I haven't tried to sell you an upper at all, let alone this setup. This leads me to believe that you (or someone) are simply trying to start some SH*T. For another thing, baffle strikes are a possibility with any mount, any suppressor, anytime,anywhere. I'm never going to guarantee that it won't happen. |
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