View Full Version : LMT's new gas key staking is...odd. What are your thoughts?
DreadPirateMoyer
04-27-16, 16:34
Foreword: I already contacted LMT about this to make sure it's in spec. It is.
I recently ordered some new parts, among them two of my chosen BCG: the LMT Enhanced BCG. Upon opening the box and inspecting the new BCGs I received, I noticed something weird. Specifically, the staking is wonky. It's not necessarily wonky in a bad way, but it was weird enough compared to what I'm used to (Colt, BCM, and LMT BCGs) for me to contact LMT themselves. Pictures below.
http://i.imgur.com/x7gQAxR.jpg
From the top, the gas key staking looks weak compared to Colt, BCM, and past LMT BCGs I own. It doesn't go over the fasteners and only makes contact with the sides of the fasteners. It leaves me with a distinct lack of confidence.
http://i.imgur.com/2jC8xZ0.jpg
From the side is where it gets really weird. It doesn't have just the usual staking marks at the top of the key, but rather two sets of staking marks: one set like we're used to seeing at the very top of the key, and one set right below it, as if LMT is staking not just the top of the fasteners, but somehow the bottom as well. I seem to doubt that the bottom set of staking is deforming the key enough to make internal contact with the fastener at that position, but without taking it apart, I doubt I'll know.
(For the record, both BCGs look exactly the same as these pictures, so I don't think it's a one-off mistake or a QA/QC problem)
Because of how unusual this seemed to me, I contacted LMT and also sent pictures. They told me all was normal and not to panic; they've changed how they do their staking, and this is what it will look like from here on out.
What do you guys think? Does any other company stake like this? What do you think the reasoning could be for switching from the old method? Do you think the bottom set of staking actually does anything, and if so, could this be why they no longer stake the upper set enough to go over the fastener but just enough to make contact with the sides?
Curious as to what everyone thinks. It stood out to me for sure.
I am not kidding when I saw this and thought, That looks just like my Spinta BCG staking. I don't know much about the technical specs behind staking, but it looks a little half-hearted. it may be better than the old way. Who knows?
I think that Rob_S has done all of us a significant disservice by making such a big deal out of something that is remedied in about 30 seconds with a vise, a hammer, and a punch and probably isn't a big deal in the first place.
Flankenstein
04-27-16, 16:39
Weak and looks like shit but will be fine.
39185
I like this from LWRC, seems like a great idea.
LMT is a quality company. They say "it's good to go", I would just run with it as is. You could put some "witness marks" on it and check it now and then.
DreadPirateMoyer
04-27-16, 18:41
I am not kidding when I saw this and thought, That looks just like my Spinta BCG staking. I don't know much about the technical specs behind staking, but it looks a little half-hearted. it may be better than the old way. Who knows?
Yeah, might be better than the old way. I can't see why they would change it if it weren't an improvement, because the new staking doesn't look like it would be cheaper to do.
I think that Rob_S has done all of us a significant disservice by making such a big deal out of something that is remedied in about 30 seconds with a vise, a hammer, and a punch and probably isn't a big deal in the first place.
I don't know on that one. I think it's a pretty big deal and have seen fasteners loosen before (not from a quality BCG). On top of that, while it is easy to remedy, it is indicative of the quality of construction/commitment to detail of the company. Even if it's not a big deal, a company that misses this crucial step is not paying attention to what they should be and likely have missed or not taken care of other things too.
Then again, this is all a can of worms that has been rehashed many times before.
39185
I like this from LWRC, seems like a great idea.
Not a fan since the entire gas key can't actually be replaced should anything happen to it.
LMT is a quality company. They say "it's good to go", I would just run with it as is. You could put some "witness marks" on it and check it now and then.
True, and I'm going to do that as I don't have much other choice at this point, but it's still a fairly odd deviation from standard. I'd like to know if anyone knows why and if it's a good or bad deviation. Insight, essentially.
Not a fan since the entire gas key can't actually be replaced should anything happen to it.
What would happen to it, there is less parts to break, the majority of the key is part of the BCG metallurgy? And if anything happened to the tube receiver part, it could be replaced. Pretty obvious to me it's an improvement, less parts, no staking to worry about, just one roll pin.
LWRC removed the normal gas key from their original piston BCG due to breakage. More force is exerted on that spot with the piston design and the remedy is to make the key part of the BCG. The DI key has less energy exerted so in actuality this would be over built for purpose intended.
556BlackRifle
04-27-16, 21:15
It's hard for me to see in the pics but it looks like there's more surface contact between the fasteners and the stake than you get with the traditional method. LMT isn't going to put out crap. I'm sure it's GTG.
Rayrevolver
04-27-16, 21:35
There is a spec for staking and I bet most places over stake. Although I am not sure what negative impact pushing up the extra material has on the gas key or operation of the BCG.
If material is touching the head on both sides I call it good.
I have seen so many crapping stakings and keys loosen over the years, it's a big deal. Of course, it's not a big deal if you only shoot a few rounds and then stick it in your safe. The torque spec is low, which is why the staking is even more important.
I think that Rob_S has done all of us a significant disservice by making such a big deal out of something that is remedied in about 30 seconds with a vise, a hammer, and a punch and probably isn't a big deal in the first place.
Upwards of 75% are actually doing it poorly.
There is a spec for staking and I bet most places over stake. Although I am not sure what negative impact pushing up the extra material has on the gas key or operation of the BCG.
If material is touching the head on both sides I call it good.
I have seen so many crapping stakings and keys loosen over the years, it's a big deal. Of course, it's not a big deal if you only shoot a few rounds and then stick it in your safe. The torque spec is low, which is why the staking is even more important.
The OP could have solved the problem, if there is a problem, in the time it took to make that post.
The OP could have solved the problem, if there is a problem, in the time it took to make that post.
If this turns out to be a bad staking job then it shows shitty QC and/or bad business decisions. It's not the OPs job to fix his rifle. Its LMTs job to produce a good rifle. Not saying they aren't.
If this turns out to be a bad staking job then it shows shitty QC and/or bad business decisions. It's not the OPs job to fix his rifle. Its LMTs job to produce a good rifle. Not saying they aren't.
You're right. The OP could send that rifle in to LMT and require that they fix it, but LMT saw the pictures and said there's no problem. LMT's a good company. I'd be inclined to take their word for it over a group of internet gunsmiths. If I was worried about it, I'd rather just get out the hammer and punch. Seems like that would be simpler than packing up the rifle and sending it back for warranty work for a problem that LMT says doesn't exist.
DreadPirateMoyer
04-28-16, 06:52
The OP could have solved the problem, if there is a problem, in the time it took to make that post.
You're missing the point of the thread. It's not about this being a problem or not. It's about what people think about the change.
Good/bad? What could be the purpose of the second set of lower staking marks? Why change at all?
The purpose of the thread is discussion on the change, because it's not standard and it's both interesting and weird. On that point, you've made your opinion known multiple times. Thanks.
.46caliber
04-28-16, 07:03
Time and round counts will tell if the new method provides better, equal or inferior retention. If I were you Moyer, I'd either witness mark and run up the round count to test or re-stake and forget it.
My initial thought after seeing the pics is that they're working a new method that allows faster and more consistent staking. Like they've designed a jig that holds two floating punches in position, maybe with stops to prevent the punches from over travel. Drop the assembled carrier in the jig, two whacks of a hammer and the staking is done. No hand holding punches and the stake is in the right spot every time.
Has the OP contacted LMT?
It's GTG. Looks to me like they are grabbing a lot more meat a little lower on the hex bolt. Typical staking, "punch style" deforms the key in a way that the part of the key that is deformed by the staking process is torn, stretched & stressed. I would liken it to the difference between jerking off with just your index finger & thumb, or, using your whole hand.
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DreadPirateMoyer
04-28-16, 07:55
Time and round counts will tell if the new method provides better, equal or inferior retention. If I were you Moyer, I'd either witness mark and run up the round count to test or re-stake and forget it.
My initial thought after seeing the pics is that they're working a new method that allows faster and more consistent staking. Like they've designed a jig that holds two floating punches in position, maybe with stops to prevent the punches from over travel. Drop the assembled carrier in the jig, two whacks of a hammer and the staking is done. No hand holding punches and the stake is in the right spot every time.
Yeah, I think witness marking it and running it is about the best I can do at this point in terms of real world stuff. I might just have to be the guinea pig for the forums and report back after a year or two.
Has the OP contacted LMT?
The OP (me) stated twice that he did...did you even read it?
What would happen to it, there is less parts to break, the majority of the key is part of the BCG metallurgy? And if anything happened to the tube receiver part, it could be replaced. Pretty obvious to me it's an improvement, less parts, no staking to worry about, just one roll pin.
LWRC removed the normal gas key from their original piston BCG due to breakage. More force is exerted on that spot with the piston design and the remedy is to make the key part of the BCG. The DI key has less energy exerted so in actuality this would be over built for purpose intended.
Quick search came up with this pic. Not a LWRC but similar design. Cool design but time will tell.
http://uploads.tapatalk-cdn.com/20160428/e7c6a31e3320efdec733391d4a779615.jpg
They're staking at top (side) of key and mid-barrel of the screw -- more metal displaced to keep the screw from turning.
You could also stake from the top using the GI field method described in the TM -- but that would certainly be over- overkill.
http://i135.photobucket.com/albums/q125/PursuitSS/Bolt%20Carriers/85c19690ba958fcd3d5ffca4602ebba9.jpg
Yeah, I think witness marking it and running it is about the best I can do at this point in terms of real world stuff. I might just have to be the guinea pig for the forums and report back after a year or two.
The OP (me) stated twice that he did...did you even read it?
Sorry, guess I missed LMT's response.
Sample size of one, and not an SME, but I have always been pleased with LMT's commitment to quality. Since they have stated that this was a deliberate change on their part, I would presume there is a good reason. However, I certainly don't discount the OP's initial concern. If I saw something vastly different than what I was expecting, I would probably have asked them as well.
Sample size of one, and not an SME, but I have always been pleased with LMT's commitment to quality. Since they have stated that this was a deliberate change on their part, I would presume there is a good reason. However, I certainly don't discount the OP's initial concern. If I saw something vastly different than what I was expecting, I would probably have asked them as well.
And that's totally justifiable. I don't care how much I pay for a product, $5 or $5k, its getting an inspection. $10 PMAG from magpul gets a look over. I say +1 for the OP in posting a change. LMT isn't cheap, and people who buy their products probably are this in depth when looking at detail.
I have removed two carrier keys from newer LMT Enhanced carriers with this new style of staking. The screws with this new staking were much more difficult to remove compared to how they used to stake them... I would say the screws were about twice as hard to remove vs. their old method.
This is all by the feel of my uncalibrated arm&hand, I did not use a torque wrench.
Has anyone used a calibrated dial type torque wrench to remove the fasteners from a newer LMT staked offering to see if their retention is sufficient?
Removal torque and applied torque are some of the important things to look into for the key fasteners. Sometimes visual indicators are misleading.
Gas keys and their fasteners sounds simple, but there are many things that can come into play.
It's also not the point. Not notifying the manufacturer and holding them accountable if an error was made is why we have sub par stuff on the market.
The OP could have solved the problem, if there is a problem, in the time it took to make that post.
For this example, it is normal to see differences from different sources. Going by a visual inspection alone is not sufficient to be able to determine if the said sample component is adequate, or inferior.
Some samples may not be my preference, but still do very well while a better visual inspection may not yield the same results.
Quick search came up with this pic. Not a LWRC but similar design. Cool design but time will tell.
http://uploads.tapatalk-cdn.com/20160428/e7c6a31e3320efdec733391d4a779615.jpg
That's broken, so.... pretty good example of why a removable key is preferable.
DreadPirateMoyer
04-28-16, 20:48
Incoming wall of text...
They're staking at top (side) of key and mid-barrel of the screw -- more metal displaced to keep the screw from turning.
You could also stake from the top using the GI field method described in the TM -- but that would certainly be over- overkill.
That was my thought as well. I thought for sure the mid-barrel stake wouldn't be able to displace metal inside of the gas key at that location, but the more I read from this thread, it looks like my thoughts were wrong. And true, if they do ever loosen in the field and I need something to solve the issue immediately, a field stake could do it on the overkill level. :)
Sorry, guess I missed LMT's response.
It's ok. I get defensive on the forums, but I usually call people out on not contacting the manufacturer as well. :p
I have removed two carrier keys from newer LMT Enhanced carriers with this new style of staking. The screws with this new staking were much more difficult to remove compared to how they used to stake them... I would say the screws were about twice as hard to remove vs. their old method.
This is all by the feel of my uncalibrated arm&hand, I did not use a torque wrench.
That's good to hear. Between you and sinister, that seems to confirm that the mid-barrel stake is actually doing something.
For this example, it is normal to see differences from different sources. Going by a visual inspection alone is not sufficient to be able to determine if the said sample component is adequate, or inferior.
Some samples may not be my preference, but still do very well while a better visual inspection may not yield the same results.
Definitely true. There's a lot of people out there (including in this thread) that know way more than me, so was hoping to see if anyone knew anything beyond the visual inspection I did. The visual inspection is definitely not enough to make a good decision.
And that's totally justifiable. I don't care how much I pay for a product, $5 or $5k, its getting an inspection. $10 PMAG from magpul gets a look over. I say +1 for the OP in posting a change. LMT isn't cheap, and people who buy their products probably are this in depth when looking at detail.
Yup! Thanks to you and winch and everyone else for understanding. LMT makes great products and I feel like they wouldn't make a change for no reason, but just because of that doesn't mean they don't make QA/QC or design mistakes. It's definitely a deviation from the norm and was worth discussing, I thought (just like when they switched to MIM/nitride keys a few years ago, which turned out to be nothing in the end).
I've seen a few posts from IG on other venues about gas key staking, and it's more important than people give it credit for.
And that's totally justifiable. I don't care how much I pay for a product, $5 or $5k, its getting an inspection. $10 PMAG from magpul gets a look over. I say +1 for the OP in posting a change. LMT isn't cheap, and people who buy their products probably are this in depth when looking at detail.
Totally agree. I have an LMT, and would do the same thing.
Stake or steak , it's LMT and looks good to me. Good observation but gtg.
Quick search came up with this pic. Not a LWRC but similar design. Cool design but time will tell.
http://uploads.tapatalk-cdn.com/20160428/e7c6a31e3320efdec733391d4a779615.jpg
Honestly, that looks like a cheesy design, very thin in the area where it broke. Apparently Salient has more R&D to accomplish. LWRC's looks much beefier and they didn't make it 100% monocoque like salient did, perhaps that's the issue with the salient version. Or maybe a manufacturing defect, which is possible.?
Like I said before. Lwrc designed theirs in that fashion because of the broken keys due to the extra force of the piston rod. The new DI bcg kept the main body of the key area then they just added the tube, still all the force is on the main body of the key area. This design is holding up and has held up for some years now. LWRC in my opinion in every bit as good as LMT, they make a quality product and have for sometime. Don't knock them because they make a piston gun, they are a well respected and well deserved AR manufacturer always looking to get more life and reliability out of an already reliable original design.
It's ok. I get defensive on the forums, but I usually call people out on not contacting the manufacturer as well. :p
I am mostly interested in info over anything, certainly would love to hear their side of the story.
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