Howdy Sig crew!

I am building out my MCX collection and am trying to figure out which route to go:

1) 1 MCX with multiple barrels and handguards (6.75, 11.5, 16) and keep it all in a hardcase cut for the parts. If anyone has a photo of their setup that would be awesome.

2) 3 MCXs 6.75,11.5,16

3) 1 Rattler with two handguards (Standard, and Sup) and 1 MCX with multiple handguards and barrels(11.5 and 16)


Currently I have a Rattler and a Legacy MCX

I am not a fan of the mcx but it seems to have a good reputation now. I guess the answer to your question is: it depends. What would be your applocation for the carbine/carbines? If you would use mostly one barrel lenght over the others i suggest ypu to buy only one mcx with 3 barrels. Consider that you would have to rezero the rifle everytime you change the barrel.

I have the MCX with 4 barrels - 6.75, 9, and 16 in .300, and 16 in 5.56. I didn't plan it out that way, I originally had the 9" to sbr it, but then the 6.75 came back in stock so I fo'd.
And I have 3 handguards, the original and two shorter suppressor width ones.

All range toys and like to have options for short, med, long. You do make a good point about rezeroing. Something I did not think about.


Which 2 do you use the most? Is rezeroing everytime you swap annoying? do you wish you had multiple? Do you keep all of them in a a single case?

Rezeroing can be Time consuming Only the first time If you take note of the Clicks you need to get to every configuration!

I personally wouldn’t trust it. I wouldn’t feel any method of mounting optics/sights setup will faithfully repeat zero every setup transition.

I keep hearing the MCX doesn’t have a super repeatable zero upon barrel uninstall/reinstall. I don’t know as my Rattler doesn’t really accept any barrels but the one it’s got, so when I branch out my MCX I’ll be getting a Virtus upper either way. I know it’s possible with repeatable torque though, at least in other designs. My MWS is repeatable as well as I’m able to tell.

I wouldn’t expect every barrel to have the same zero, that would be silly. But I’d really like if each barrel were repeatable to itself. Then you could just pair each barrel to a complimentary optic on a QD mount, or record adjustments on a single optic for each barrel. But if each barrel isn’t repeatable upon being pulled/installed, that really takes a lot of appeal out of the whole idea.

I would do it for a range toy. Of course i wouldn't rely on this method for a difensive gun

I agree 100%

Op,

I have a 11.5 virtus upper, a 16 inch virtus upper, and a 9 inch legacy 300 blackout.  I am not a huge fan of barrel swapping and optic mounting/re-mounting.  I dont think your zero will change drastically if at all, i dont know because i never tried it with the virtus barrel change system.  I have done it with a LMT MRP and it held zero after a barrel change, but its not something i do often.  I always just preferred to have several uppers with different barrels and optics zeroed to that upper.

I've left the 6.75 on there, so no swapping yet. it's mostly a safe queen at this point but when I get to a better location I plan on getting to shoot it much more. I have no professional use for it, so I can't speak to how it is day-in, day-out.
I expect the rezeroing to be a little annoying, but I've heard that it is pretty consistent if you make sure everything is tight when you swap.
I would like to get a virtus as well, but that's a ways off.

@jle57, you have a good question and one I am dealing with as I am getting into the MPX and MCX platforms.

One of the main selling points is the modularity and end user customization of the gun for certain uses and setups. Quick change hand guards, barrels and stocks/braces is one of the draws of the platform for most of us.

However, as others have said, it is a bit of a pain to have to swap barrels in and out and re-zero (or trust your old zero) for optics. I have read corregon state the re-zero of handguard was fixed in the current MCX and does return to zero. Barrel supposedly has good return to zero as well, but have also heard some guys state it doesn't.

So I guess you could have certain optics zero'd for certain barrel calibers and lengths. I would recommend you should still check your zero. Use of multiple barrels does get the most out of the platform in terms of the modularity design of it.

Or, having multiple complete MCXs does make life a lot easier; grab and go. Especially if you plan to use the certain setups often. If you are only going to have 1-2 setups that you will use the vast majority of time, and then have extra barrels as backups or for setups you won't use as  much, I can see benefit of swapping barrels in and out. Really just depends how you want to use the MCX platform. There isn't a right or wrong way in that regard. Just depends on what you want out of it, your budget, how much room you have in your safe...etc.

Is it only a few clicks for your setup? Do you find you wish you had another upper?


Guess you would need multiple uppers for deticate optics for it to work?



Yeah I like the idea of a modular setup, but how it works in practice as im seeing now dont know if it makes sense.


Ive seen some of the goods youve posted in the virtus/mcx threads, motivated me to get the SD rail for the Rattler! I have pretty much given in, but trying to Marie Kondo my toys hahaha and have a handful and use extra funds for NVGS :)


Yeah thats where it looks like it is going. Its the compromise between barrel/handguard vs complete setup



THANK YOU! Makes sense for all of the 2 mcx setup in the votes. 1 Rattle for ultra compact, and 1 mcx to do 11.5 and 16 inch setups.

You can get a separate Virtus upper for $450-500. Slap a second barrel and optic on for a different niche.

Could possibly get a BCG, as well.

True! So you are saying go the multiple upper route?

At some point.

I’ve pulled the 6.75 barrel out of mine plenty of times and never had issues with zero.  Always spot on with T2 aimpoint.

3 uppers are 1 lower.  

Rezeroing the optic with every barrle change will be a pain in the butt..  

I have a MCX Legacy I bought as a 11.5" 556 pistol and added 9" and 6.75" 300 blk barrel.  Then I added a Rattler.  

I carry a Virtus 9" SBR for my patrol rifle.  There are few changes (some may claim improvements) over the Legacy.  I believe two are worthy and they are the rear of upper is thicker and the gas system is easier to access and maintain on the Virtus.  

I have not shot my 11.5" barrel or the 6.75" barrel.  The Rattler is a little loud unsuppressed.  I run a Dead Air Sandman K on my MCX guns and it is reasonable.  I wanted the shortest can and am happy with what I have.  

I would always recommend a 556 barrel to help expand your ammunition selection in hard times.  Plus if you are going to a high round count course you can save a little by running 556.  You will be running the same gun and many courses of fire won't challenge a caliber change.  

I like the idea of a Legacy/Virtus with a 9" blk and 11.5 (maybe 16" if it's your thing) 556.  Plus a 300 blk Rattler.  You basically have a spare lower.

Mike