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Sig LVAW, MCX, Virtus, Rattler, and Spear-LT series FAQ (Page 3 of 3)
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Does the MCX Spear LT upper absolutely require the use of the MCX Stock Adapter to use on an AR15 lower? I read a review that said you could plop the Spear LT upper onto an AR lower but it just would look weird since it sits up taller. I was wondering about how the MCX recoil rod would be supported or interfere with an AR buffer. |
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Originally Posted By metroplex: Does the MCX Spear LT upper absolutely require the use of the MCX Stock Adapter to use on an AR15 lower? I read a review that said you could plop the Spear LT upper onto an AR lower but it just would look weird since it sits up taller. I was wondering about how the MCX recoil rod would be supported or interfere with an AR buffer. MCX: Generation 3/SPEAR LT |
On ne voit bien qu'avec le cœur. L'essentiel est invisible pour les yeux.
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Thank you! The photo makes sense! Has anyone found any torque values for the MCX stock adapter? In a few other threads, someone called SIG and they told them to snug everything up - no torque values. Someone else said their Virtus armorer's manual say 70 in-lb for the bumper screw (which seems excessive). To me the buffer adapter has that wrench flat, and its design makes me think torquing to 40 ft-lb ala rifle buffer extension should work? The bumper screw, probably 40-45 in-lb? I did find all of the other screw torque values (for the screws I could find). Handguard Link Screw 2400439-R, #8-32, 10 in-lb (as per SIG as well) Cam Path Insert Screw, 2400180-R, #6-32, supposedly 35 in-lb according to SIG, but that seems like way too much torque for a steel 6-32 screw let alone SS. Forward Assist Screw, 2400438-R, #4-40, 6-8 in-lb according to SIG, but I saw someone's armorer manual excerpt showing 10 in-lb w/ Loctite 222. |
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@SpyHawk I saw this on the forum the other day: https://www.ar15.com/forums/armory/MCX-Generation-3-SPEAR-LT/45-534561/&page=39#i6011026 I also saw a while back that someone was asking about the MCX uppers being larger than standard AR lowers (can't find it on the search and don't remember which sub-forum it's in). I took a few pictures of what Virtus and SPEAR-LT uppers look like on a standard AR lower. I didn't see this in your first post and SIG themselves haven't really talked about it. The Virtus and SPEAR-LT uppers are significantly "wider" and protrude out over the sides of the lower receiver when using a standard AR. I have not run into any function issues using either upper on the AR lower, however, the forward assist housing screws are clearly visible when mounted on a standard AR lower. MCX VIRTUS [LEFT] - S&W MP15 [RIGHT]  MCX VIRTUS UPPER on MP15 LOWER  MCX SPEAR LT UPPER on MP15 LOWER 
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Yes, that was me. Thank you! I've heard this referred to as the muffin top. It's actually not that bad - it only hangs over part of the lower. My issue is that my lower receivers have always been "in-spec" with AR15 uppers. Meaning whether it is an Aero, LaRue, or early 2000s RRA - the lowers always fit nice and tight, no issues. But the MCX Spear LT is more finnicky as the part that faces the front takedown has limited clearance. AR15 uppers for the most part don't have anything covering the front takedown lugs of the receiver. So there's no clearance issue. After much investigation, it seems the lowers have a little too much material at the front that interferes with the MCX Spear LT upper. I don't see a reason for them to make the uppers with this limited space. These are the scalloped areas near the 2 roll pins and feed ramp insert. However, another problem I'm now encountering is the handguard link is too tight because once the handguard screws are tightened, the handguard link tilts a little making for a very tight fit of the pin. I need to use a tool to push it out otherwise I am not able to remove it like on an AR15 upper. I tried loosening the HG link screws and HG screws, slipping the takedown pin through (easily slides through) and then tightening all of the screws - but this results in the pin being really stuck. Is this normal? Does SIG want to use the HG Link to essentially keep everything snug (especially the HG)? can I ditch the HG link if I use the Arisaka ZRC? |
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The gas regulator for the Spear LT 11" barrel is a JM01 Low Side port: 0.064" (recessed/slotted) High Side port: 0.059" Also the SIG taper adapter will not completely cover the shiny taper exposed when you remove the factory Clutch-Lok flash hider on the MCX Spear LT.  |
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Originally Posted By SpyHawk: Question: How do I change the dust cover on my Sig MCX series weapon system? Answer: You must remove the forward assist/case deflector assembly to replace the dust cover. See below for details. A much easier way (in my eyes, since I have had those tiny forward assist screws strip on me more than once - and one Virtus receiver I have has “tamper-proof” screws in there) is to fully loosen the barrel clamp, remove the barrel, and then drive out the roll pin on the bolt-head side of the barrel clamp (the pin that retains the bolts). This will allow the barrel clamp to pop off and you can then easily slide the dust cover rod forward on the receiver like you would on a standard AR upper. There is even a small slot in the bottom of the forward assist that you can get a small pick into to help push that rod forward to get it started. I just used this method tonight to remove one from an LT upper to switch it to a different cover. |
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Originally Posted By metroplex: The gas regulator for the Spear LT 11" barrel is a JM01 Low Side port: 0.064" (recessed/slotted) High Side port: 0.059" Also the SIG taper adapter will not completely cover the shiny taper exposed when you remove the factory Clutch-Lok flash hider on the MCX Spear LT. https://i.imgur.com/12lUMBU.jpg Originally Posted By metroplex: The gas regulator for the Spear LT 11" barrel is a JM01 Low Side port: 0.064" (recessed/slotted) High Side port: 0.059" Also the SIG taper adapter will not completely cover the shiny taper exposed when you remove the factory Clutch-Lok flash hider on the MCX Spear LT. https://i.imgur.com/12lUMBU.jpg Confirm that your orientation of the taper adapter is correct. |
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| I saw something online regarding the silencers that may be "MIL/LE". Maybe someone here can confirm. If the box starts with a "W" in the model number that this indicates it is MIL/LE. For example, my SRD762Ti-10 has "WSRD762Ti-10" written on the box. Is this a mil can? Or do the real mil cans have "mil" etched on the can? |
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Originally Posted By Omega9000: I saw something online regarding the silencers that may be "MIL/LE". Maybe someone here can confirm. If the box starts with a "W" in the model number that this indicates it is MIL/LE. For example, my SRD762Ti-10 has "WSRD762Ti-10" written on the box. Is this a mil can? Or do the real mil cans have "mil" etched on the can? Any SIG SKU that begins with "W" is a MIL SKU. You may also see "L" SKU's, which are Law Enforcement. |
On Time. On Target.
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Originally Posted By Omega9000: I saw something online regarding the silencers that may be "MIL/LE". Maybe someone here can confirm. If the box starts with a "W" in the model number that this indicates it is MIL/LE. For example, my SRD762Ti-10 has "WSRD762Ti-10" written on the box. Is this a mil can? Or do the real mil cans have "mil" etched on the can? I've seen one up close. Can't speak to the box, but the model on the can itself is MIL-SRD762Ti-10 |
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Originally Posted By Omega9000: And… day ruined. What are you trying to accomplish? One thing you will notice with us is that you can see a wide-range of markings, SKU's, packaging, etc. Especially for a long-running program, SKU, etc. There are several answers that might be "right". |
On Time. On Target.
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Originally Posted By coregon: What are you trying to accomplish? One thing you will notice with us is that you can see a wide-range of markings, SKU's, packaging, etc. Especially for a long-running program, SKU, etc. There are several answers that might be "right". Not trying to accomplish anything in particular. I was just hoping to have something kind of neat. My collection has started to move more towards these small but cool little differences. But that is besides the point of this thread. That being said, since there are many variations of "right". I'll take that as a win. Thanks again. |
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Originally Posted By Omega9000: Not trying to accomplish anything in particular. I was just hoping to have something kind of neat. My collection has started to move more towards these small but cool little differences. But that is besides the point of this thread. That being said, since there are many variations of "right". I'll take that as a win. Thanks again. Originally Posted By Omega9000: Originally Posted By coregon: What are you trying to accomplish? One thing you will notice with us is that you can see a wide-range of markings, SKU's, packaging, etc. Especially for a long-running program, SKU, etc. There are several answers that might be "right". Not trying to accomplish anything in particular. I was just hoping to have something kind of neat. My collection has started to move more towards these small but cool little differences. But that is besides the point of this thread. That being said, since there are many variations of "right". I'll take that as a win. Thanks again. Yep, sounds good. You will see things, somewhat, all over the board. Some products are exactly the same, with the only differences being commercial vs MIL vs LE SKU's, some things are different, many MIL/LE units utilize COTS (Commercial Off The Shelf) purchasing habits (which is another curveball in the clone world), etc. Are you seeing a "W" SKU but not the "MIL-..." markings on the can itself? |
On Time. On Target.
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Originally Posted By coregon: Yep, sounds good. You will see things, somewhat, all over the board. Some products are exactly the same, with the only differences being commercial vs MIL vs LE SKU's, some things are different, many MIL/LE units utilize COTS (Commercial Off The Shelf) purchasing habits (which is another curveball in the clone world), etc. Are you seeing a "W" SKU but not the "MIL-..." markings on the can itself? Yup. “W” SKU but no MIL marking on the silencer. The box has an Apr 2017 date and has all the commercial branding (not the brown non-descript box) The can is unfired. Exeter,NH engraving. |
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Originally Posted By Omega9000: Yup. “W” SKU but no MIL marking on the silencer. The box has an Apr 2017 date and has all the commercial branding (not the brown non-descript box) The can is unfired. Exeter,NH engraving. Originally Posted By Omega9000: Originally Posted By coregon: Yep, sounds good. You will see things, somewhat, all over the board. Some products are exactly the same, with the only differences being commercial vs MIL vs LE SKU's, some things are different, many MIL/LE units utilize COTS (Commercial Off The Shelf) purchasing habits (which is another curveball in the clone world), etc. Are you seeing a "W" SKU but not the "MIL-..." markings on the can itself? Yup. “W” SKU but no MIL marking on the silencer. The box has an Apr 2017 date and has all the commercial branding (not the brown non-descript box) The can is unfired. Exeter,NH engraving. Can mean several different things - may have just been the way the SKU was set and was sold into the commercial market that way, could have been earmarked to go to an LE agency ("W" used to denote anything NOT commercial, that has changed since 2017), could be several different reasons. |
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Originally Posted By coregon: Can mean several different things - may have just been the way the SKU was set and was sold into the commercial market that way, could have been earmarked to go to an LE agency ("W" used to denote anything NOT commercial, that has changed since 2017), could be several different reasons. gotcha. I appreciate you helping my try to determine if my can was mil overrun or not. Either way, great can. Don't have anything to put it on but it sits proudly in my collection. |
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Hello, I hope this hasn't been answered in the trove of information here, but here I am: Would a MCX canebrake upper work with a regular AR15 lower? I assume it's not a simple yes/no question, but if it is no, I will not pursue the acquisition of said upper. Additional question, I assume the fake can is screwed on the barrel. But when removed, does it expose a tapered portion of the barrel like on the LT barrels? If so, I'll have to acquire a Sig Muzzle Device Collar for MCX .300 AAC Models as well before being able to mount the muzzle device (non Sig) of my choice. Thanks! |
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Originally Posted By Ur77Meteorit2: Would a MCX canebrake upper work with a regular AR15 lower? Originally Posted By Ur77Meteorit2: Would a MCX canebrake upper work with a regular AR15 lower? But when removed, does it expose a tapered potion of the barrel like on the LT barrels? Yup, the barrel is tapered. The Canebrake comes with a taper adapter so you can use cans/muzzle devices without a taper. |
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Originally Posted By bChau: Originally Posted By Ur77Meteorit2: Would a MCX canebrake upper work with a regular AR15 lower? But when removed, does it expose a tapered potion of the barrel like on the LT barrels? Yup, the barrel is tapered. The Canebrake comes with a taper adapter so you can use cans/muzzle devices without a taper. Much appreciated. 
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I am back again with my random questions.  Browsing this thread and doing some research on the internet, I cannot really find a definitive answer as to whether an AR15 trigger would work with a Virtus upper. Specifically, an ALG ACT trigger, which is what I am running in my AR lowers. I saw some mentions of removing a part of the BCG, mentions of hammer height but nothing definitive. Or maybe it depends on the “age” of the Virtus upper? Thanks again for any insight. |
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Originally Posted By Ur77Meteorit2: I am back again with my random questions. Browsing this thread and doing some research on the internet, I cannot really find a definitive answer as to whether an AR15 trigger would work with a Virtus upper. Specifically, an ALG ACT trigger, which is what I am running in my AR lowers. I saw some mentions of removing a part of the BCG, mentions of hammer height but nothing definitive. Or maybe it depends on the “age” of the Virtus upper? Thanks again for any insight. Sadly no. You would need to remove the firing pin safety latch for it to work. Which, a lot of people do. And it's basically fine. Just don't use any super soft pistol primers in your 300blk ammo. If you have money to spare, it might be worth picking up a Spear-Lt bolt carrier group which has a different firing pin safety that is compatible with all AR hammers. |
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Hello fellow oddities lovers, I recently got my hands on a Rattler kit (complete barrel + handguard). It was a catch and release. When I tried to look up the kit, all I can find to match the handguard design was this pistol.  Now, SIG does have a Legacy Rattler caliber exchange to go to 5.56, and it does come as a 5.5 inches long barrel. https://www.sigsauer.com/mcx-rattler-5-5-replacement-barrel-5-56nato.html My question is what barrel length do I have on my Rattler? From the pictures below, I'd say 4 inches from the barrel mounting flange to the tip of the threaded section. Because it is definitely shorter than the other barrel (which I measured with the same start and end at 5.5 in indeed).   Unless I am measuring from the wrong place, I had never heard of a 4 inches barrel in the Rattler family.  Any insight or correction would be greatly appreciated. |
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Originally Posted By jwlaxton: If I have an MCX Virtus 5.56/300BLK and want to swap to the Spear LT carrier group to allow more choices in triggers, do I need a different op-rod or recoil springs? Just pop out the firing pin safety. It's super easy to do and will allow you to use other triggers. |
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Originally Posted By sbye: Just pop out the firing pin safety. It's super easy to do and will allow you to use other triggers. Originally Posted By sbye: Originally Posted By jwlaxton: If I have an MCX Virtus 5.56/300BLK and want to swap to the Spear LT carrier group to allow more choices in triggers, do I need a different op-rod or recoil springs? Just pop out the firing pin safety. It's super easy to do and will allow you to use other triggers. I'm familiar with the assembly and will have to remove it to re-use the recoil springs/op-rod with the Spear LT carrier. I had heard/read that the recoil springs might be different with the Spear LT vs Virtus because of weight differences of the carrier, but according to the small parts shopper on Sig's website, they are the same. I bought one, so will see if/how it works. Worst case I also have to buy the new Op-Rod. The only thing I really like better about the Spear LT over the Virtus is the ambidextrous bolt catch on the lower and the new design of the carrier group. |
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I have a 11.5" Virtus with a pinned & welded silencer that I'm thinking of upgrading to a Spear-LT. However, this means I need a suppressor handguard which is big enough to allow a 1.5"-diameter silencer through it. I'm using a Midwest Industries suppressor handguard on my Virtus, but there doesn't seem to be an equivalent Spear-LT handguard available. 1. Does anyone make a rifle-length Spear-LT suppressor handguard? or 2. Could I use the Virtus suppressor handguard that I already have on a Spear-LT? |
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The primary weight difference between the LT carrier assembly and the post-recall Legacy/Virtus assembly are the recoil guide rods. The pre-recall and LT recoil assembly have aluminum recoil guide rods that weigh roughly 1.82oz less than the steel rods used in the post-recall assembly. The post-recall OP rod weighs less than the LT OP rod if the firing pin safety latch, plunger and spring are removed. The LT bolt carrier is lighter than the post-recall carrier even with the firing pin safety latch installed which, if you run a LT bolt carrier in that configuration, you can keep or remove if you choose. From what I understand, the spring that's on the firing pin is ANOTHER firing pin safety feature. The LT's tapered firing pin is about half the weight of the post-recall firing pin (less than 1g lighter). The LT's cam pin weighs about 3.5g less than the cam pin in the post-recall assembly (it's shorter and has larger relief cuts). I'm not sure if there's any difference in spring weight because I don't have any LT springs that aren't pinned in an assembly. |
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Originally Posted By LeeTN: So, how does it differ from the stock Rattler .300BLK SBR? Suppressor handguard? Originally Posted By LeeTN: Originally Posted By sbye: Sig just dropped a new SKU that looks to be their civilian LVAW on an LT upper. https://tombstonetactical.com/product/sig-mcx-ltaw-300blk-6.75-sbr-bk-30r So, how does it differ from the stock Rattler .300BLK SBR? Suppressor handguard? It says it comes with an inert silencer. It seems to me that this may be the LT generation of the old Tacops. I kind of wish they would do another one-stamp like the original SUR300. Like, do a 9" with a permanently attached Hexium and properly gassed valve and SD handguard. |
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Originally Posted By ayyyota: There's an additional transitional upper for the gen1 with 4 slits (plus the adjustment holes). It's pretty rare from what I've seen looking at public photos - maybe overrun from contracts? Hmmm... I'm not sure because I've never seen that upper in person or picture. The Gen 1.5 in my pics was from a true Gen 1.5 MCX. It shipped from SIG on an M400 lower w/ MCX adapter. I sold the M400 lower and adapter and put the upper on a MCX lower. I'm sure that'll make some collectors lose their minds! I don't have the LT or Virtus uppers anymore so I can't do any further comparisons of all the different uppers but, I still have a few Legacy uppers and the 1.5 upper. I'll get some better pics of the two side-by-side and post them here at some point. |
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Originally Posted By WITTSER83: Hmmm... I'm not sure because I've never seen that upper in person or picture. The Gen 1.5 in my pics was from a true Gen 1.5 MCX. It shipped from SIG on an M400 lower w/ MCX adapter. I sold the M400 lower and adapter and put the upper on a MCX lower. I'm sure that'll make some collectors lose their minds! I don't have the LT or Virtus uppers anymore so I can't do any further comparisons of all the different uppers but, I still have a few Legacy uppers and the 1.5 upper. I'll get some better pics of the two side-by-side and post them here at some point. Originally Posted By WITTSER83: Originally Posted By ayyyota: There's an additional transitional upper for the gen1 with 4 slits (plus the adjustment holes). It's pretty rare from what I've seen looking at public photos - maybe overrun from contracts? Hmmm... I'm not sure because I've never seen that upper in person or picture. The Gen 1.5 in my pics was from a true Gen 1.5 MCX. It shipped from SIG on an M400 lower w/ MCX adapter. I sold the M400 lower and adapter and put the upper on a MCX lower. I'm sure that'll make some collectors lose their minds! I don't have the LT or Virtus uppers anymore so I can't do any further comparisons of all the different uppers but, I still have a few Legacy uppers and the 1.5 upper. I'll get some better pics of the two side-by-side and post them here at some point. I have such an upper (ETA: maybe it's just a legacy, as I see a few of them on Google photos). Got it off Gunbroker several years ago from a guy parting out a MCX. Used as a LFaux base (though I have the SRD762-Ti Long Boi with a Lancer handguard and Gen 2/Virtus internals):  |
Sig LVAW, MCX, Virtus, Rattler, and Spear-LT series FAQ (Page 3 of 3)
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