A few months ago, I placed an order for an 11.5 inch Virtus upper.  The online store's photo showed the upper came with a trigger and a lower receiver conversion kit.  When I received the upper, I only received the complete upper with no trigger or conversion kit.  After receiving, I looked on the website, and the stock photo was changed to just the complete upper, with no lower conversion parts.  I'm guessing the place where I bought this did not update their stock photos???  The missing parts are $250 in value. I haven't called to ask about this yet as I think SIG discontinued the complete conversion kits.

I planned on using an Aero ME41 lower receiver with this upper. I've had the lower for a year, and it's just collecting dust.  I plan on buying the MCX lower conversion piece from SIG and the SIG folding pistol brace.  I have spare lower parts that I can use until I save for a better trigger and an ambi selector.

My question is, do I need anything special with regards to the trigger?  I've read older forum posts, and it seems the MCX requires a firing pin lock?  Also, there are a few other parts for the lower which I'm not sure about.  The SIG stock adapter does come with a buffer--not sure if I should order some spares to have on hand.  And, I saw a parts diagram that showed a wedge for the lower--also, not sure if that is necessary.

So, I guess my question really is, what parts do I need to buy for my lower receiver to work with a SIG MCX Virtus upper?  

I think that if you got the LE/mil kit, it doesn't come with those parts. I only mention that because I see it's from Proven Outfitters.

Does it happen to have a chrome lined barrel? Not always 100% indicative of a LE kit though.

It could be the LE kit. It was not listed as the LE kit. This was the description:  MCX Upper 11.5" Barrel AR Conversion Kit, 5.56 NATO, Tapered Lug, MLOK [Sig Sauer]

The site was the only site that had the complete kit shown for sale--other sites listed it as discontinued.  I can't tell if the bore is chrome lined.

No, Sig Sauer has not discontinued the conversion kits.

I called them last week about this and the response was that they are still being produced.  If you purchase an MCX Upper (Virtus or Rattler), you should receive the conversion kit parts as well.

What’s the SIG pn on the box? UAMCX or WUAMCX or LUAMCX

I actually just looked on proven outfitters site. It’s the WUAMCX which is the export/mil/gov/le sku. No trigger or conversion parts in that kit.

To answer your real question though. You need an MCX/AR 15 stock adapter
In stock $99

Any MIL SPEC AR-15 trigger will work. Not every trigger that will work in a mil spec aR-15 is a mil spec trigger. The most important Thing is hammer profile and then spring weight. There’s a firing pin safety latch which is why MCX requires specific triggers. Hammer profile.

My upper was listed as WUAMCX-11B-556BLK-TAP

I would have lost my shit. Contact them.

Why?

He bought the SKU that corresponds with just the upper, and the posting from the vendor literally says:



It is what it is.

I hate it when the pictures are wrong or misleading but I've been around long enough to know better. If the price was appropriate for what you received I would just move on. Since they changed the pic it sounds like they probably had someone else with the same issue. All online stores should have the factory part numbers in the description so you can know what you are getting. The real issue is that the manufacturers screw it up just as often which is where a lot of these guys pull info and pics from.

Description included trigger and adapters when I purchased it.

That sucks. I would definitely try and figure it out with the company.

I sent them an email. I'm not trying to throw any company under the bus, I wasn't aware of the name in the photo I posted above. It was a quick edit on an online photo. The original photo had the company's name, which I cropped out....didn't realize the name was still in the photo.

With regards to the item description vs what I received, the wording did include the trigger, lower receiver adapter, and a folding stock adapter (to screw a buffer tube into).  With regards to the price, this company has several things at prices lower than competitors.  This was part of the reason I chose them.  The other reason I chose to order from them was this kit was listed as "out of stock" but "backorderable".  Every other place had it listed as "out of stock" but "discontinued".  Again, I wasn't sure if, perhaps, they were still the ability to get the complete kits.

With regards to the SKU, it never crossed my mind.  The description and the photo showed everything I wanted.

With regards to the parts I'll need, perhaps I should call SIG.  I never contacted their service/technical department, so I'm not sure how well that will go--really depends on the knowledge of the person on the other end of the call.

**I just removed the name of the retailer.  Again, I wasn't trying to throw anybody under the bus.

What did you pay for it? I ask because I need the same upper to go along with my SIG lower.

Roughly $1,300 shipped

Question 1:  Do they have any more in stock?  If the answer is yes...

Question 2:  Can you IM me the retailer name & URL?

I bought a 300 BO upper kit from Sig last week and it came with the folding knuckle, the stock adapter, and the trigger.

Were they in stock? I would love to find a 9” 300blk.

They were out of stock.  I placed my order in June or July with the knowledge that it would take a few months for the order to be fulfilled.

Thanks for info. I back ordered one today and Proven confirmed 90-120 days.

I bought and assembled the remaining parts for this upper.  Almost forgot about the post, and decided to post an update.  

I did contact the company.  They stated they had the wrong info listed and apologized. I don't know what the price for a complete upper normally is.  Looking at Sig's site, the MSRP is $1,600+ for a complete upper without the lower receiver adapter and trigger (for 11.5 inch 5.56 Virtus).

I had an Aero enhanced lower just sitting around. It was transferred as a firearm, so I could choose to do what I wanted with it when the time came.  I bought the lower during one of Aero's blem sales in 2019.  Can't remember the price....maybe $50? (pre-transfer and shipping fees).

For the lower, I tried one of the generic Botac Tactical ambi mag releases.  It was difficult to lock the mag, so I switched it to a spare Sig ambi mag release that I had bought from Optics Planet last year (they had them incredibly cheap at one point).  Went with the Radian ambi selector and Sig match dou trigger group.  I used a lighter trigger spring I had left over from Geissele Rapid Fire trigger.  The spring is too light for the Geissele (for me at least), but works perfect for the Sig trigger (spring from Sig was a little too heavy for my liking). The trigger pull is great now, but the trigger shoe on the Sig digs into my finger (annoying distraction).   I went with the Sig folding pistol brace to keep the length of pull under 13.5 inches.   For an optic, I currently have a Primary Arms Cyclops (taken from another rifle).  Not really sure what type of optic set up I'm going to use.  For now, the PA Cyclops works.

Total cost for everything (sans optic) was about $1,800.  It is the most I've paid for a firearm to date.  I took it out to test everything and sight in the optic.  I have to say, it shoots really nice.  From my experience with AKM variants, I expected the Sig brace to smack my cheekbone uncomfortably--it didn't.  I usually like something with more of a cheek weld, but the thin brace didn't bother me while shooting the pistol.  The arm brace portion was initially tight until I opened it up. Now, it spins freely, but this doesn't bother me at all.  I don't like the amount of money I spent on this, but it functioned amazingly well.  I expected it to beat up my cheek, or to be a little rough due to the size--it was neither.  The only problem I had was it did not cycle fully on the Wolf .223 ammo on the low gas setting.  Bolt did not lock back on last round, and I had one instance of bolt riding on top of round.  I think it did lock back when I opened up the gas though.

Thanks for the update.

Very nice looking setup.  I'm hoping to create something similar, but with a Gearhead Works Tailhook installed on the Sig Brace.

Try the brace first.  Some people complain about it spinning. But, it honestly doesn't bother me.  It may down the road, but it didn't bother me the day I took it out.  It didn't spin so freely until after I opened the brace up. Prior to, it was very tight.

Nice man. I have a 80 lower I am going to do a 6.75 BO build on.

That looks horrible. You should sell the upper to me...??