Handling the MPX at NRA last year kinda killed the telescoping stock for me. It was a bit difficult to use one handed IMO. I do like the stock style that comes on the MCX, I just hope the durability isn't going to be an issue on that hinge plate. An adjustable LOP version would be great down the road.

After handling one at Cabela's yesterday, I was really considering getting one.............those pics of the broken stock kinda made me change my mind a bit. Hopefully that issue is worked out. It's a nice handling rifle. And I see there is an option for the solid, side folding stock..........might be a better choice for that rifle.......I think I will give it a little more time for more reviews and may wind up getting one of these. I definitely like the caliber change option

This is probably one of the more novel features of the MCX and one that's likely to draw a good bit of attention, especially since the gun is available as a "kit" with both a 5.56 and a 300BLK barrel.  While I have to admit a certain amount of interest in the changeable barrel idea, I don't really know how much practicality such a feature has.

As I understand it, the interest in QD AR barrels come from a military requirement to use captured enemy ammunition when operating behind enemy lines or when working in a country that fields something other than 5.56.  While I can see a good amount of benefit to that, I don't really see the application from a civilian standpoint.  Sure, it would be nice to have the ability to use one platform with multiple calibers but each barrel/caliber change is either going to require an individual range session or an accompanying optic on its own QD mount.  Another option might be to zero a red dot for one barrel and the BUIS for another but that wouldn't be ideal.

With that said, I would really like to see SIG or another company sell an integrally suppressed 300BLK barrel with an OAL of sixteen inches.  This would give the handy length and handling characteristics of a suppressed SBR with only one tax stamp.  It would also mean the rifle could be transported across state lines without notifying the ATF. The suppressed barrel could be removed for cleaning or maintenance or removed if desired and replaced with a conventional barrel in 7.62x39 or 5.56 or whatever.

This whole line of reasoning is ridiculous.

In reality i see "quick change barrels" as a way to tool on guns. Right now with the AR you need a torque wrench vice blocks, and a decent amount of time to swap barrels.

A qc barrel is what i would term "user serviceable" and requires a single preset torque wrench and about 30 seconds.

For large, high round count organizations this is a massive cost decrease when doing trainups.

For individuals, it allows them to swap lengths and make repairs without the need for a whole workbench full of tools. Add an optic with a rtz QD mount and you significantly reduce the cost of needing a whole upper assembly (which is 85% the cost of an AR).

I hope the aftermarket picks this up. I'd love to have choices from the plethora of quality AR makers. I'm fairly certain SIG will be pouring massive support behind this gun; they see this platform (mpx/mcx/mcx-mr) as the future of the company, unlike the XI which even during development i felt was an afterthought. (I was explicitly told the 55X series will end with the XI to focus on the MCX).

I think the "user serviceable" idea certainly has merit and the idea that a shooter or an armorer can configure a rifle to a specific role or task with minimal tools and effort is a good one.

I guess my complaint with the whole idea is more of marketing. Not that SIG is doing this but some companies have advertised the QD barrel as something that can be changed on the fly. I recall reading something from a year or so ago where someone wrote that you could be perched on a roof with your 6.5 Grendel in an overwatch capacity. Then redeploy to a CQB role with a suppressed 300BLK and then finish the shift with a .458 SOCOM barrel while manning a vehicle checkpoint.

So I understand the value in having a multi-role firearm but I don't think its realistic to expect to be changing out barrels while "in role."

I think a lot of that dates back to the Masada introduction. The Masada with its built in QD assembly and handle pushed that idea, despite the fact that it's absurd.

Not to mention I can just see getting .300 and 5.56 mixed up in the field producing some exciting results.

 
0.62"

Well, I found one.  Should be here Thursday.  Can't wait!

I saw the rail section at the end of the top rail is attached to the handguards lower half and not the receiver's extended toprail. How securely does the bottom handguard lock in? Maintaining zero concerns me.

I'm not certain, because I don't have one, but in this pic:

 

I don't like that Sig is only going to sell the 6.5" blackout barrels to LEO/MIL

Ideally SIG will sell the piston and gas parts so owners can source their own barrels in 5.45, 6.8, 204 Ruger, .277 Wolverine, etc.

They said that isn't the case on Instagram.

On Instagram Sig said it's actually 6.75" and it will be sold to civilians. I'll believe it when I see it. It's really the only option I'm interested in as my PWS Mk110 meets and exceeds my 5.56 needs.

I figured that's what he was getting at anyways, 1/4" wouldn't be a real significant difference.

I do hope they sell the blocks so aftermarket barrels are viable. No barrels being available is what really took the wind out of the sails of the ACR(not that the other fuckups with it helped either).

I can't wait to see handguards made available.

KMR or Samson for the MCX would be sick

Nope, you're exactly right.  

 

The channels are tight and the fit is secure when the handguard is installed and the pivot pin inserted.  No wobble whatsoever.  

The majority of the top rail is part of the upper receiver so I'm not concerned at all about holding zero with an optic.

Do you gents know if the lower will be available separately?

I wouldn't think so since I don't think the lower is backwards compatible with a standard AR upper.

Well then, looks like I will be buying a MCX.  They talked about how they taper the barrel to keep their suppressors from backing off.  Do you think my AAC Cyclone will stay on, even though it doesn't have a taper built in?

I would very much like to know this as well.

Someone posted a rough video of what is involved with swapping calibers.

https://www.youtube.com/watch?v=fHfSoWp6uGc

Nice job on the sound. I guess his pickup mic is across the room? I only watched until he said he hadn't read the manual. That was enough for me.

I said it was rough.

Still, it does show how the recoil assembly comes apart which was my biggest question having not yet received mine.

Anyone know if this is legal in MI? A Wisconsin cabelas would not transfer one they had to my FFL here in MI. ATF admin for them cited a conflict in MI vs Federal law about OAL being under 26" when folded.  Cabelas website has the OAL at 26-7/8" folded. I'm assuming that is including the FH.

So, the Sig guy was pretty impressed with the broken stock when we called for an RMA, he said it's the first one coming back. I'm going to make a certificate for my coworker for being the first person to break an MCX in the world

We got four pistols in today. The arm brace folds to the side too.......

Same hinge mechanism?

Pretty sure it's different. Looks like a locking button mechanism vs the MP5K-style assembly on the rifle. Hopefully I'll have one in hand soon to take better pictures.

 
If you have any questions feel free to ask.




As far as the manual is concerned it leaves a lot to be desired and really doesn't address caliber changes aside from the process of changing barrels. The way I figured out how to remove the op rod from the BCG was to examine the spare and see that there was a spring loaded pin that had to be depressed which meant disassembling the BCG to access the pin through the hole on the bottom. Not a big deal but something you would expect to be explained in the manual.






 

Completely different.

This is the button to fold it




It attached via a picatinny rail on the back of the lower.

http://www.gunbroker.com/Auction/ViewItem.aspx?Item=468414564

Must have gone fast.  Nothing showing.

Broken link. Try this.

http://www.gunbroker.com/Auction/ViewItem.aspx?Item=468414564

Buy it now for $2,900!

Thanks for fixing my broken link.

Both the auction start price and buy now prices are too high but at least the guns are showing up at places other than Cabela's.

My dealer just called. It's at his place. I'll pick it up late tonight or tomorrow, whenever his schedule opens up.

I'm like a damn kid at Christmas.

Well, Xmas finally came. Upon delivery, I was had a bit of anxiety as I opened the case. The outer cardboard box looked fine but everything inside the case was a mess. The extra barrel, mag, op rod, manual and rifle were pretty much all slammed together toward one side. I'm not sure if fedex dropped it or if the foam in the case just sucks but nothing held its place from what appeared to be normal shipping and handling.  I was relieved to find everything inside to be as it should. No scratchs or dents. I was immediately impressed by the weight and balance.  Right off the bat I noticed some degree of slop between the upper and lower despite there being a spring loaded "wedge".

It was late in the afternoon before I was back home.  It comes with the .300blk barrel on so I needed to swap things around. That went smoothly. I threw it on the scale empty to find a weight of 6lbs 13.4oz. Outfitted with a EOTech and 30 rounds it came to 8lbs 9oz. Again, the weight is very nice and balances extremely well.

I didn't have time to do any accuracy testing but I was able to run about 300 flawless rounds through it.  The last few hundred were suppressed. As far as gas to the face, if a DI AR (without gas buster handle) is heavy, this was moderate. The tapered muzzle worked just fine for my direct thread can.

I do not like the extended selector on the right side. That will definitely be getting swapped out for something with less of a profile. It digs into my trigger finger. Also, as most everyone has noted the trigger is horribly heavy. That will be swaped out ASAP.  I will also swap out the FH for a brake. It shoots pretty flat as is but it is not to the level of a PWS MK116 with a FSC556 brake.

Overall, I am favorably impressed. If it holds up over time I will definitely sink a ton of money on it. I would really like to SBR it and grab a short 7.62 barrel, short .300blk barrel, short handguard and a new .30cal can.

Well, this computer seems to be acting up. I'll link some photos from my phone in a minute.




Internals after 300 rounds, 200 of which were suppressed.




Tapered barrel.




Handguard pin attachment.




Extended selector that I do not like.



Nice roll marks.




On the scale.



With some other gen3 friends.

Got my pistol yesterday.  Had it engraved before I picked it up and the form 1 will be sent out early this week.

Here's my current setup for now.



Pulled the terrible trigger and threw in my SSA-E.  I also added a MOE+ and will be upgrading the safety soonish.  I was gonna add a Raptor but the charging handle is slightly different.

Swapped the springs out of some lighter weight ones that I had laying around. Also installed a normal selector. Much better.

Ran somewhere around 300 more rounds through it. No issues. Everything seems to be wearing in nicely.

From the sounds of things, if I have my SBR lower setup the way I want (grip, selector, trigger) I would be better off just buying the conversion kit when it comes out...

Thank you, sir.

So, it's almost like an M16A1 profile... almost.

That will be out in about...3 years. Can anyone tell me if the MCX upper will fit on a standard AR lower without modification from a "conversion kit"?

It will not fit without the conversion kit.

Thanks. What would need to be in the conversion kit to make it work?

The MCX upper receiver is different dimensionally than a standard M4 upper receiver - in terms of the height of the receiver.  See the picture I posted below and I think it will make a little more sense, in terms of how "deep" the lower receiver cut is to accept the MCX upper.

The kit will come with a plug for the receiver extension on a standard AR lower and plate to act as a backstop for the recoil springs.

Here's a picture of the MCX lower, shows what the adapter plate will look like for a standard AR lower to plug the receiver extension and recesses for the recoil plugs

http://soldiersystems.net/blog1/wp-content/uploads/2015/02/FullSizeRender-440x470.jpg

Can't embed images from SoldierSystems anymore for some reason, but that shows the AR adapter piece.

Must be something on my computer, works fine on mobile.

Posted Via AR15.Com Mobile

You had it the first time - at least, at one point you had it, I saw it