Sig MCX Virtus

[74novaman]

People talk about about how modular the AR-15 is. And that's true, it's a very versatile gun, especially using multiple uppers.

But when it comes to just one individual gun with no extra receivers being versatile, the Sig MCX is the next generation of "modular". The Magpul Masada (turned ACR) had potential, and the MCX is a fully fleshed out take on it, IMO.

Here's a stock photo of what they look like:


Thick handguards and lack of a buffer tube are two obvious differences. MCX uses an AR-18 style piston and dual recoil spring assembly, eliminating the need for a buffer tube. G36, SCAR, Bren, etc all use similar AR-18 derived set ups. That means folding stocks are an option, which is nice.

Here's just the upper and lower:


Pic rail lower means any stock that attaches via 1913 rail can be used on the MCX. The extended upper receiver has rails for installing free floated handguards. Instead of a traditional barrel nut, MCX uses a clamshell style clamping mechanism to hold the barrel. With nothing more than a T27 torx bit you can swap out stocks and barrels. They have 5.56 barrels in 16" and 11.5", and 300blk barrels in 16", 9", 6.75". Rattler has 5.5" barrels in both calibers but stuff is slightly less interchangeable between the MCX and Rattler so I'm just focusing on MCX, though the Rattler is neat too.

And here's just one way you can set up an MCX: as a small PDW.



Close up of barrel install: you'll notice notches in the receiver to match lugs on the barrel to help line everything up consistently.



The underside of the receiver has a notch for the handguard retainer, which is held captive by the front take down pin (pretty smart design). Thanks to the long rails on the receiver that the rail installs on, anything like a peq that needs to hold zero can go on the handguard no problem.





And all slapped together. Took about 3 minutes.



Size comparison with a full size handgun to show how small this thing really is:



It's nice having something barely bigger than a handgun that can sling 300blk.

I'll follow up later with some other ways you can set it up. It's a very neat design and I think you'll see a lot of other companies doing similar things in the future. Modularity just makes too much sense. If you get a chance to pick up an MCX, I highly recommend it. They're really fantastic rifles.

[cmgee67]

They are very cool guns for sure! Nice rigs! Thank you for the information

[74novaman]

They are very cool guns for sure! Nice rigs! Thank you for the information

No problem. Its neat to see a potential attempt at a next generation rifle to me. The AR has been so dominant and so well developed by both mil and civilian side that it almost seems like nothing will ever take over for it, but super modular guns like the MCX might if anything ever does.

[cmgee67]

I’d like to see something take over and replace the AR-15. I like them and I personally think they are the best all around rifle that has ever been made. But the prob that has started to show is, that they have pretty much taken that particular type of rifle as far is it can go. Something modular like the sig is the next progression

[Paladin]

What kind of accuracy are you getting out of the MCX?

[Rafe]

SIG is one of the last three companies in the running to be selected for the Army's replacement of the M4, the M16 and the M249. My bet is that they have a really good chance.

The offering previously from General Dynamics is now being handled by a company called Lonestar Future Weapons. Theirs is a bullpup design, I believe for both the AR replacement as well as the M249. Not certain about that, though.

The other entrant is Textron Systems. And it's one ugly gun...but it isn't a beauty pageant. The real reason I'm selfishly hoping against Textron is that theirs uses what they call "caseless telescoped ammunition." This has a polymer system encased the bullet, shortening the overall length but providing the same ballistic capabilities. May work just great. But it's such an oddball ammo that I could envision supply chain issues (not that the federal government ever has any issues with that), and it isn't something that we're likely to see on the shelves at Academy any time soon.

All are chambered in 6.8x51mm (bullet about 135 grains; around 3,000 fps). Which I think makes sense (those supply chain issues aside) because I do believe it's time to replace the beloved 5.56. Super great for its time when boots on the ground had to lug their own ammo through the jungles of Viet Nam. But it's always been just a little too anemic for the kind of firefights we saw in the sandbox; just doesn't have much effective range. I love me some .308, but that's a little on the large side for an individual infantryman to carry in any volume.

SIG's entrants, though, the NGSW-AR lightweight belt-fed machine gun and the NGSW-R rifle, are...ta dah!..."built on the foundation of the battle-tested MCX platform." To me, I think there's a big benefit to be gained from the new battle rifles having both the MCX modularity and a not-too-dissimilar manual of arms compared to the M4/16. And since SIG has a huge marketing footprint in consumer sales, those military developments/improvements are likely to quickly filter down to civilian models. I mean, when was the last time you bought a Textron or General Dynamics firearm? The ammo won't be Academy-ready from the get-go, though. It isn't as odd as the Textron offering, but it's still a hybrid case design. The case walls are traditional brass, but the base that joins it is (I think) an aluminum alloy. It's alloy of some kind, at least. The design allows the rifles to retain backward compatibility with standard brass-case ammo while, according to SIG, provides a weight savings of about 20-30% per empty case.

As probably everyone predicted, the Army has pushed their selection date from "by 2022" to "by mid-2022." We'll see. But if SIG is selected, I expect that will give them a big development budget bump and a big consumer sales bump. I've been really trying to keep my number of calibers to a minimum, preferring to have more of a few than a little of a lot. If someone wanted to give me something in .50 BMG or .338 Lapua Mag I wouldn't turn it down, but... All I shoot nowadays in rifles is 5.56 and .308; don't really hunt deer anymore so sold my last "other" chambering, a .270 Winchester bolt gun, a few years ago, and I don't do LR benchrest. But...I should start putting my spare change in the piggy bank because I know that if SIG wins the contract, as soon as the NGSW-R and the ammo become available to consumers, I'm gonna want one.

Here's a pic of one of the prototype SIG NGSW-R MCX Spear assault rifles:

[Scott B.]

My MCX SBR is my primary. Not an inexpensive system to get into but it's rock solid.

Word of caution when you have your barrel out. The #1 way people break their barrel clamps is that they don't notice the dust cover pin has moved forward and tighten the clamp over the end of the pin. That pin is captured by the clamp and can slide forward when the barrel is off.

Also a note on the NGSW bids. Reportedly Textron has withdrawn and I can't see the US Mil ever going w/ a bullpup. Might leave only one standing.

[Paladin]

These tests don't show any accuracy improvement over a MILSPEC AR-15 barrel: Tested: SIG Sauer MCX Virtus Patrol Rifle

[powerboatr]

thats impressive,
the lower looks much easier to change out barrels
i have a stag arms ar 10 that can be barrel swapped from 308 to 6.5 creedmoore, but its a PIT rear area to swap barrels,

thanks for sharing

[74novaman]

These tests don't show any accuracy improvement over a MILSPEC AR-15 barrel: Tested: SIG Sauer MCX Virtus Patrol Rifle

Given how accurate good ARs are, thats not exactly a bad thing.

Reflects my experience using factory ammo, both 5.56 and 300blk. On par with my quality AR barrels.

[Rafe]

Also a note on the NGSW bids. Reportedly Textron has withdrawn and I can't see the US Mil ever going w/ a bullpup. Might leave only one standing.

I think I'd be just fine with that. I'm useless to comment because I've never shot any of them, but it's a lot easier for me to trust one from SIG based on the MCX--even with hybrid ammo--than prototypes that always looked like...well, prototypes. I've also never met a bullpup trigger that I particularly liked. 'Course I haven't actively been trying to test a bunch of them, either. Love the concept of short OAL but long (relatively) barrel, but it seems to me no one has yet figured how to make the firing mechanism as smooth on the trigger as a conventional barrel-forward platform.