As title states, I’m wondering what y’alls thoughts are on the MCX and it replacing the ar in some cases. I’ve been into ARs ever since I got into shooting and hunting for the most part. I’ve built several setups, but lately it seems the MCX is everything I’d want an AR to be, and for less hassle and money.
So, should I finish the 16" syrac piston build I’m doing, or go MCX?
What does the MCX do for you that an AR doesn’t? Besides be new and neat and different?
I trust Sig Exeter to make a decent rifle about as much as I trust Obama to look out for my well being.
Piston, quick change system, ff sights, warrenty, folding stock,
The piston is a plus why?
Looks like you already made up your mind
If you prefer it for you, that’s fine. If you really want a piston setup - uh, OK, why exactly? Notice that New Zealand just adopted the DI LMT MRP as its new army-wide issue rifle, in a competition that was otherwise mostly piston designs. And I doubt that the LMT was cheaper.
I continue to like the AR over other designs because:
-extremely well proven after 50 years
-completely debugged after 50 years
-truly standardized parts so I can replace any part of any typical AR15 with parts from dozens of other manufacturers
-ease of maintenance and repair
I cannot overemphasize the standardization of parts. So many cool designs fail when they become unsupported. I had a Robinson Arms M96, which is an awesome design, but the manufacturer stopped supporting it in just about any way when they moved on to the XCR. It was one broken part from being an expensive paperweight. Likewise many new cool designs will be rare show pieces in 20-30 years or sooner - think ACR, most piston designs other than the SCAR (I’m hoping FN will support that into the future, and they actually have a good track record), any Bushmaster proprietary design, etc. etc. But for now and the foreseeable future you can get any part for an AR15; you can do the same for a FN-FAL, AKM, or HK91 clone, though with fewer sources, but some one-off proprietary cool design from 20 years ago - good luck. I look at guns as long term equipment purchases (not quite an investment but not a disposable either) and I like to hope they’ll be useful long into the future. Very, very few proprietary designs get to that point.
How is it on standardization and availability of parts and after factory support? Armorer’s classes? How well has it proven itself with law enforcement and military groups?
never heard of it 
I like the MCX and MPX and plan on owning them. My question though is, why do you need a piston or the quick change capability? Are you really going to change out the barrel?
C4
After having changed a lot of barrels, rail systems etc. I like the idea of it being much simpler. The piston is a preference mainly by my father who has always preferred piston systems. Galil, ak, m14, mini14 etc. I finally got an osprey system in a trade and have since become a fan myself.
I’m not a huge piston fan, but I like piston guns. Even more so when the gun is originally designed to use a piston. I love the AR’s ability to be easily fixed, upgraded, modded etc. At the same time, I’d love a rifle that out of the box is exactly how it will be. Take it out the box and leave it alone.
Why would anyone want to move the piston of their AR from the carrier where it gets to stay cool and lubed and move it to the gas block where it will be hot and dry?
Do you think there will be a lot of rail options available for the SIG like there is for the AR?
Pistons have their place, but generally only shine with FA/Suppressed use. There are also down sides (more weight, less accuracy, hard to get spare parts, more expensive, etc).
There is no free lunch.
C4
I’m a little wary of Sig, but I’d like to have an MPX to add to my collection.
As far as replacing the AR, well, others have pointed out the advantages of the AR. But I also like reliable piston rifles and the only piston rifles I’d rely on are the SCAR rifles. Even with their ergonomic shortcomings they are really good rifles and I think they will be supported for quite awhile. That’s not to say that some of the other piston rifles are not reliable, I’ve not owned them, but I trust the SCARs. And I don’t like the AR/Piston Hybrids.
I guess a “good luck” is in order. Recent SIG commercial rifles have a poor record for reliability.
Certainly an op-rod piston design has an advantage when it comes to running suppressed, but the issues that arise with the Stoner design can be mitigated greatly with an adjustable gas block. Outside of suppressed use, there is no advantage to an op-rod piston rifle.
I’m not big on quick-change barrels – I prefer having quick-change uppers. I have multiple AR uppers, all with optics already mounted and zeroed to them, that I can use either on my fixed stocked or my collapsible stocked lower for any conceivable role. It will probably be years before replacement barrels for the MCX will even be available, and they will almost certainly cost more than building an AR upper. That has definitely been the case with the SCAR.
A folding stock is something I have never personally placed much value on – it is hard for me to see why it would ever be so critical for the rifle to be able to fold another 8" shorter for transportation or storage – but if you do have a peculiar need for that capability, products like the LAW folder can give it to you with an AR.
Sights mounted on the free float handguard are nice in a way, since you can get greater sight radius with a longer handguard, but they have the disadvantage of POI shift under handguard pressure. In any case, you can have it either way with the AR. With the MCX, you are stuck with only handguard-mounted sights.
What’s better than a warranty is a rifle with plentiful and cheap spare parts, any of which can be easily replaced with simple tools at home. Instead of sending it off for a month or more, you can have it back in business the same day, or in the time it takes for parts to ship. As I eluded to, there is a real good chance of needing that warranty on a SIG rifle.
Forgot to mention this will be used with a suppressor. Curious what the blow back will be like with the MCX
If you want the MCX because you want one, great, go ahead and get one. Obviously you won’t be alone. But it doesn’t seem to have any compelling benefits (if in fact any benefits) over the tried and true AR. This forum doesn’t tend towards validation of choices (unless your choice is Colt or BCM), so I wouldn’t expect any endorsement of the MCX as “better” here. But it’s still a somewhat free country and for now you can own a dozen types of rifles “just because”, and many of us do. I have some random stuff just because I like it, though I’m limiting how oddball since I don’t want anything to be a pricey and regulated paperweight down the line when parts dry up. YMMV, offer not valid in Kentucky, Canadian residents may be required to pass a skills test before claiming prize, etc. etc.
Do you think PWS pistons are likely to be headed down the road of unsupport? I mean no
way to ever know, but what are your thoughts? Not trying to hijack the thread either.
In slightly bitter experience, here is my two factor test for future support:
Opinions can vary but for #2 I would put FNH-USA and Ruger as the only manufacturers with consistent and deep support across several decades, although S&W has done an excellent job for its revolvers (but not all other products) and Glock has done a decent job on their small and focused product line. No slight is intended to KAC or LMT, but I’m not sure they are old enough, especially for civilian sales, to have a usefully long track record. And DD is much younger still. In time I expect they will also prove themselves, but it’s not like you can buy a 1950’s manufactured product of one of those makes.
So with that said, I would not rely on future support of PWS, even though I think they are, as of today, a good company with good products. Only a handful of firearms makers are actually big companies with a broad product line, and most of those are either defense contracts (FNH) or leviathans of the sporting market (Ruger).
How many people actually have any significant hands on time with either of these two provide some kind of informed opinion?