So now, the part you’ve all been waiting for?



But, appreciation comes only with context.

Like the MCX, to understand the MPX we have to go back in history. We’re setting the dial on our time machine back to 1964: to the birth of an icon (no, not Sandra Bullock or Elle Macpherson, but close). For as long as it’s existed the Heckler & Koch MP5 in 9mm has been the gold standard, bar none, of submachine guns. The MP5 is a double-title holder in that the MP5SD (integrally suppressed variant) is also the gold standard of what a suppressed production gun should sound like.

The MP5 was a roller-locked delayed-blowback submachine gun chambered in 9mm, .40, and 10mm. It was accurate, smooth, easy to control, light for its time, and well-liked by military units and police agencies throughout its tenure as the submachine gun of the free world. The MP5 came to fame when it stared in a certain SAS operation against Iranian terrorists in 1980. It also featured largely in various movies like Predator and Die Hard, and even long-running TV shows like Stargate SG-1. Unlike the UZI, which was probably its closest global competitor, the MP5 was easy to mount optics on, fired from a closed bolt (more accurate), and, to a degree, was more modular in terms of grip/grip frame and stock options. The MP5 set the bar, and a very high bar at that, for what a submachinegun could and should be.

If the MP5 is still the gold standard in so many ways what happened to it? To put it bluntly, HK got tired of it. They may still support the 9mm platform in some respects, but a large part of their corporate emphasis shifted to the UMP, which is a direct-blow-back, polymer framed submachinegun (ca. 1999) of entirely new design. IMO, the Universal Muppet Pistol is a simpleton-pretender to the throne and a wholly unworthy successor to the MP5.

If you ever want to know what a cycling UMP feels like you can build a UMP action for yourself, from household materials. What you will need are three things: 1) a large brick, 2) a shoebox, and 3) the ability to put the brick in the shoebox and shake it back-and-forth. While the UMP offers a less expensive and lighter overall package due to its polymer frame and a simplified blow-back action (I did say it was a simpleton), it lacks the ethereal smoothness of its predecessor. Smooth is both accurate and fast, which is kind of a big deal in the spitting-distance world of the submachine gun.

To be entirely fair to HK, the UMP came out at a time when American law enforcement was also getting tired of pistol caliber carbines as a genre, and moving from PCCs to short-barreled rifles. The military application of pistol-caliber carbines was always very limited to spec-ops and POG types (an ironic juxtaposition in some ways). Furthermore, HK had a lot of other balls up in the air including the MK23 and G36, both of which were arguably more successful in their respective fields than the Oomp.

Now, on the fiftieth anniversary of the MP5, SIG is poised to introduce a worthy heir to the throne of King of Submachineguns.


The MPX debuted, for the civilian market, at SHOT 2013, where it was probably the most finger-fucked gun of the entire show, displacing other worthy entries like the IWI Tavor. But in the roiling tumult that was 2013, where the country went mad for all things black-rifle, we heard nary a peep from SIG about the MPX. Some of this could have been the fact that the MPX, unlike the MCX, is mainly driven by foreign contracts and SIG’s focus landed outside our borders. Alternatively, the focus could have been producing 516 and 716s which were already proven and imminently in demand. It could also have been that the MPX simply was not ready for public release. Finally, it could have been a combination of all three.

You could ask “why show it in 2013 and not have it ready to go?” I think that’s a fair question. I can’t really give a specific answer on SIG’s behalf, but it would seem to follow the trend of SIG learning not to sell products that aren’t ready. It’s January 2013, the cat’s out of the bag in terms of knowledge of the platform, but that doesn’t mean SIG was obligated to sell it if they weren’t confident in the platform. In the future, I hope we as consumers don’t have to be subjected to that two-year debut-to-commercial-release timeline. All I can say is I hope SIG keeps up its commitment to learn from what we as mistakes in product introduction.

Fast forward to today: even in its short history, the MPX itself has seen some rather significant incremental changes. And why shouldn’t it? It’s been around for nearly 2 years…that we know about.

To demonstrate this, we’ll go back to Corporate Display Room (we really ought to come up with a better, cooler name for that space) and look at the MPX on the wall there.



First off, the thin vertical stock is now obsolete, replaced by a 7 degree slanted stock tail. This in fact, isn’t the only version of the thin vertical stock as the MPX on Ron Cohen’s wall has the same or similar stock tail, but with a thick, presumably rubber pad added to the end of it.

Additionally, this earlier version of the MPX has some significant differences from the version I tried out on the range. I mentioned the selector in my earlier article. This is the original selector as was debuted in 2013. It is ambidextrous but features sharply terraced levers of equal length on either side. Now, when I see a selector lever than has an obligate vertical position (usually “fire”) and levers of equal lengths on either side, my reaction is usually a frown. I’m not going to say that SIG doesn’t know what they’re doing, but I would encourage anyone who thinks this arrangement is a good idea to look at their hand the next time they grasp a gun with a pistol grip and M16 style safety. Does your hand come up to the same level on both sides of the gun? No? Then why have a lever that is equally long on both sides of the gun? Doesn’t matter whether you’re a lefty or righty, one of those levers is going to gouge your trigger finger when it’s in the vertical “fire” position, especially a sharp one like on this particular MPX. On a gun like HK’s H9X series grip frames, where the lever never points towards or arcs past your trigger finger, having a long lever is not a bad idea (in fact, due to lavage issues and ergonomics, it may actually be a very good idea). But on a gun with an M16-style selector layout, seeing that makes me want to get my rasp out and go to work.



Luckily for us, the shape and texturing of the selector has been corrected in later models.

Next we’ll go under the gun and take a look at the QD socket. Now, I still agree with Lindsay Bunch that the QD slot should be a steel insert rather than a feature that is directly-machined into the aluminum receiver. But in this examination we’ll see that the QD socket on this gun appears to be part of the stock assembly rather than the receiver. Meaning that, 1) In order to have QD capability on this gun, one must have this or another QD capable stock attached 2) the QD location could change as the stock changes. In later production guns, the QD socket is moved to the tang above and behind the pistol grip. IOW, it’s part of the receiver rather than the accessory stock, allowing the universal placement and use of a sling on the MPX regardless of stock configuration or presence.

Unfortunately, prior to my going to Portsmouth, I could access no depictions of exactly where this socket was or how it looked from SIG’s side-on only photos—only a vague line pointing to where it presumably was. If I had though a little bit harder about the socket placement I would have brought along my Magpul MS4 and tried slinging/transitioning with the socket in use (specifically to see if the socket & sling combo could interfere with your pistol grip, my guess is no, but at this point it’s just conjecture). Guess I at least cannot think of everything.

Finally and even more significantly, the early MPX from the display room entirely lacks the Lancer right-side-bolt-release button.

Regardless of whether this gun has X feature or not, I think the bigger lesson is to be very careful judging internet photos of the “MPX” because, even in the room that is supposed to host examples of production guns, we’re seen things that don’t exist anymore or have been obsoleted by later production versions. So before you get into a pissing match with another internet denizen, or even SIG customer service over whether X model has Y feature, make sure you are referencing the correct iteration of the correct model.

There is in fact, talk of further reducing weight on the MPX, so even the photos that I identify as “latest model” may not be that way for long. I don’t think the MPX will change dramatically before it gets into consumer hands, but it would be unreasonable to expect it not to change a little before American consumers get to pull the trigger on it. I can also tell you now that the stock selection for the SBR and Rifle versions have not been finalized at the time I am writing this article. Here’s hoping SIG goes with my personal fav’ Kate Moss stock. She’s light, strong, solid, thin, and beautiful, and she can work any runway from Paris to Entebbe with less than 24 hours notice.

We’ll start from the front and work our way to the back on the left side, then come around to the right.

The MPX will first be released as a 9mm, though it is planned in .40 and .357 SIG. The barrel is cold hammer forged, topped off with a 13.5x1 LH thread and A1 style flash hider. SIG has five lengths of barrels planned: 4.5” (“K”), 6.5”, 8”, 8” with perm attach brake (MPXc only), and 12” + ~4” moderator (for 16+ non NFA OAL bbl length). The first three will be available in both pistol and SBR configurations upon release.

The MPXc is the model that drew so much attention in 2013, with its slant-baffled brake arrangement that could host an end-threaded cover which would cover the brake and turn it into an integrally suppressed can (threads on the brake for slip-over shell were proprietary). The MPXc’s fate is still being held up by BATFE which will rule on the model’s legality again in September.

We did not see an example of the 12+4, but it was described to me as a 12” bbl with a 4(+)” perm-attached muzzle device that looked similar to the XM177 moderators on very early M16s. This version will be rifle-specific and come with a ~12" handguard.

The MPX will ship with aluminum SIGMod handguards, but like the MCX, there are two other variations: SIGMod Carbon Fiber and Aluminum KeyMod. Handguards will come in different lengths: 4”, 6” 8” and “extended”. Early literature for the “extended” led me to believe it was 12” but that could certainly have changed by now (the only guns to use the 12” were the suspended MPXc and the never-before-seen 12+4). Handguards, will be user-interchangable.


KeyMod handguard on 4.5” K model. I did not have a QD sling swivel to see if a sling could be plugged directly into the handguard a la SLR, Odinworks and AmTac.


2” rail section on SIGMod handguard.

Behind the handguard is the beginning of the monolithic receiver rail. This rail is an extension of the upper receiver and is uniform between all MPX configurations. Below the rail, the barrel inserts into the upper receiver and is locked in place via barrel nut. The MPX will come with a wrench to access the barrel (SIG never refers to the barrel as “quick change”).

This is really good news for us as consumers. I proposed the following scenario to Jeff Creamer: “Suppose I buy an 8” MPX today, but the gun I really want is an MPXc. In September BATFE cries ‘Uncle’ and drops their objection: do I have to buy a whole new gun to get the one I wanted in the first place?” The answer was: no, just buy the MPXc bbl and long handguard and install them on your existing MPX. Unlike the MP5, the MPX is imminently modular: all the physical difference we see in terms of model (K, C, etc) are simply factory shipped non-permanent accessories to the receiver.


Adam Agri removes the handguard from the MPX. Regret: Did not get a good look at the gasblock from the angle that I was standing at.

SIG plans to release caliber conversion kits for $499, which will include bolt, bbl, and magazine. Users switching from .40 to .357 SIG would only need to purchase the appropriate bbl (and possibly handguard if they wanted to change that as well). Because the lower is the serialized part, SIG is also considering selling complete uppers.

As far as other caliber variants, we’re probably a ways out from seeing them. The 9mm will take precedence. While the .40 is probably on its way down (modern ballistic technology allows today’s 9mm to perform as well as .40s—which just take up more space and give you less rounds to solve the problem with), .357 SIG makes sense in this platform. I would be surprised if certain agencies that already use the .357 SIG round do not adopt the MPX as a replacement for their current issued MP5s, and maybe even PS90s. I heard talk of a .22lr caliber conversion, which would be appealing as the MPX has a much smaller footprint that most of today’s “tactical trainers.”

Continuing back we come to the front pivot pin. The MPX separates into upper and lower receivers in a very similar fashion to the AR. AR users will have no trouble adapting to the almost identical control layout of the MPX. The similarities between the MPX and AR even carry through to the stamping location—the lower of the MPX is the serialized part. The magazine well of the MPX features a large flare to aid in magazine insertion. Cosmetically it sports SIG’s new round logo—which would really pop if you could get some white paint down into the engraving.



I’d like to point out two curious additions in the upper receiver. The first an ovular plate, held in by two screws. We won’t get to go inside the MPX, but this sacrificial plate (like on the MCX) is our first clue that the MPX uses a rotating bolt with a cam pin. This plate takes the brunt of the punishment from the cam pin, preserving the integrity of the softer aluminum receiver. [We were able to see the bolt, but not take any photos of it. It looks like an AR BCG that’s had the back half of the carrier chopped off. The bolt has a rotating 5 lug head.] Below the sacrificial plate is a pinned-in convex piece of steel that functions as reinforcement for the chamber. Note that the display room version of the MCX does not have either of these features.

The paddle style bolt release and left side magazine release will be familiar to anyone who has a 516 or 716. Similar to the MCX, there is not much clearance around the paddle of the bolt release for bolt-on-devices like the Magpul BAD. Again, we could try a Phase 5, EBR v1, but I didn’t have one on hand to eyeball (it’s less important on the MPX for reasons we will get to later). I will say that the extended L-shape of the paddle release/stop lever is a nice touch. This increases the surface area of for the “stop” function of the lever over what is normally just small nub. The net effect is that it’s much easier to lock the bolt back on an MPX than via the standard AR button. I think this is the result of someone considering “How is this button going to be used and how can we make it do its job better?” It’s refreshing and unusual to see this in an industry filled with big names who are scared of changes and generally content to make the same thing over and over again.

SIG includes a 516-style left side magazine release on the MPX. The thing that surprised me was the lack of a paddle-style magazine release considering SIG’s touting of foreign interests in the gun. This would imply that the AR manual of arms is becoming somewhat universal, even for foreign agencies.

The MPX’s lower receiver uses standard AR trigger dimensions. Like the MCX, we don’t have a full list of triggers that will or will not work with the gun, but I will be pre-purchasing either a Geissele SD3G or Black Rain Ordnance trigger for mine (actually already have the BRO, I will at least drop it in to see if it works, even if I go with the SD3G).

I’ve already harped on the selector, so I’ll just refer to the picture here and let you decide which one you’d rather have (just note the length so when we get to the other side you can compare right- and left-side levers). At any rate, the selector is AR dimensioned so those who can’t stand the SIG layout can swap to a BADASS or potentially other aftermarket alternative.

Predictably, the MPX also has a detent-retained rear pivot pin. Everyone knows what this is for. I did not notice any wobble between the upper receiver and lower receiver on any MPX that I picked up. Whether this is a consequence of exacting tolerances and in-house manufacturing control or a tensioning pin under the upper receiver lug, I can’t say until I get the chance to open one up.

The MPX has a solid, integrated trigger guard unlike ARs, so no need for a gapper or duckbill to keep your middle finger from being torn up by sharp edges. SIG’s default pistol grip was comfortable, if otherwise unremarkable. I think some people may want to change the P/G out with a Magpul K grip or something else more customized to a PDW style gun.

Behind and slightly above the pistol-grip on later models is a built-in QD socket. We’ve already talked about this so we’ll move up to the pictinny rail. Similar to the MCX, this allows a veritable smorgasbord of stock options:

1) No stock
2) Folding tube with collapsible stock
3) Folding tube with pistol brace
4) Fixed stock of some sort (why?)
5) Telescoping 3 position 2 prong HK A3 style
6) Kate Moss


Besides the SB15, SIG is releasing a new pistol brace called the SBX which is supposed to match the aesthetic stylings of the MPX better. I don’t personally think it looks better, but option are good. This close up also shows the folding knuckle which can host AR buffer tubes and any variety of AR buffer tube based stocks.


8” MPX with folded pistol brace. (in case you want to use the brace on your left arm, iscoceles style ).

A note about Kate: the receiver of the MPX is shorter than that of the MCX. I don’t know what the interaction of the Kate stock will be with the MPX since the Kate was designed to fit the MCX and bottoms out just before the MCX’s handguard starts where it soft-locks flush against the MCX receiver. It’s possible that when the Kate is folded over the MPX receiver, the end of the stock will overlap part of the handguard. I am not certain if this will cause any incompatibilities. I was thinking about proposing a “K” version of the Kate stock that fits the MPX like the fullsize Kate fits the MCX, but that might not be very realistic given how short the MPX’s receiver is (your LOP would be about 8”). I have an email in to SIG on this, and will get back to you once I have answer.

The ambidextrous charging handle of the MPX is similar to the BCM Mod44 with latches on both sides. Like the MCX’s charging handle, it is proprietary in its dimensions.

Coming around to the right side of the receiver we come to the shortened-leg safety selector.



Moving forward from there, we’ll see the second-to-last stop on our MPX tour. The gun is mostly ambi-dexterous thanks to the licensed inclusion of the Lancer right-side-bolt release. Those with Mega or POF receivers will be familiar with what this button does. It does not, however help to lock the bolt back. I asked about why SIG did not include both features. While the MPX does mimic AR controls, SIG considers the locking of the bolt to be administrative. Including a right-side lock back feature would have meant a whole new design rather than going with a proven pre-existing system. In their defense, the only AR I’ve seen with an integrated right-side lever that locked and dropped was the HK 416 A5 (POF has a system that can drop and lock, but POF’s system uses two different buttons, one of which is inside the trigger guard—which was no-go for me).

While this is somewhat disappointing to me as a gun geek (I’m not a big fan of right-side release-only buttons on ARs either), there’s still hope that the EBRv1 will work, and even if that’s not the case, it’s understandable from a macro perspective. Most of SIG’s gov’t, particularly foreign agency clients are probably not BAD or EBR users and the right side release is an improvement on what they already have with their stock legacy M16 style systems and certainly a more ergonomic control layout than any MP5s that might still be in their armories.

MPX magazines are made by Lancer, which has a no-compete agreement with SIG. So, for at least a couple years, SIG will be the sole source for MPX magazines. SIG plans for them to retail $40-$50 but expect the market to drive prices higher than MSRP for a while. I expect a situation similar to SCAR-17, but not as bad—SIG was paying attention and taking notes and they don’t want sales of MPXs to be limited because no one can find magazines. Magazines will come in 30, 20 and 10/20 (which are permanent 10 rounders that look like 20 rounders) round capacities. SIG plans to sell the 30s singly and in three-packs w/ nylon pouch.

All magazines in the first release will in Lancer’s smoke translucent color. I talked with SIG about the possibility of a less-expensive opaque black magazine (in Lancer’s AR line, the opaques cost less than the translucents), but they’re going with one color for the foreseeable future. Speaking of costs, a lot of people are going to say “$40!?! I can buy 4 pmags for that?” Yes you could, but how many MP5 mags could you buy for that same $40? Whether we like it or not, the MPX is in a different category of firearm and one that has no legacy magazines which are already on the market and can force down the price. These magazines are also very well built by a company that knows how to make reliable ammunition feeders (90% of my operational AR mags are Lancers—I keep PMAGs for trade fodder). Quality can be expensive, but I think in the end, MPX owners will come to see that the Lancer-built MPX magazines are the match of the platform they’re paired with.

So how do they shoot?

This was, honestly, a disappointment of mine. Not in the MPX, but in the fact that the press pool had only about 20 minutes with the gun that was extended to 25 (‘cuz we’re important like that and F* your range-closure schedule, we ‘da Press ).


Note the 20 and 30 round magazines in the right hand corner.

12 press reps, 2 MPXs, 1 case of 9mm, load your own magazines.

Correspondents do you understand the course of fire?

Standby…

And the mad rush for magazines and ammo begins.

Now, the smart correspondent will do two things: 1) grab a box of ammo & a mag and get the fuck out of that dog pile. 2) Remember that MPX magazines come in three denominations, 30, 20, and 10s that look like 20s. Based on this information he should grab for magazines that look like 30s and leave the 20s for someone else who didn’t do his research.

The two demo models were an MPX K with 4.5” bbl and KeyMod handguard with KeyMod VFG, and an 8” MPX with standard aluminum handguard and 9mm “wet” suppressor (no ablative medium was used in this demo). SIG does have a 9mm “dry” can but we never saw it.


4.5” MPX K.


8” MPX with “wet” can.


Detail of the “Wet” can.

Being the tricky correspondent that I am, I grabbed for the one box of hollow points I saw, in a sea of FMJ. All of it was Aguila 124 grain supersonics (both HP and FMJ were 124 gr). I loaded a magazine with 20 HP and 10 FMJ. Any semi-auto should be able to feed FMJ, but if the MPX chokes on HP rounds, I want to know about it.

The entire magazine ran flawlessly.

Over the course of several magazines I encountered only one malfunction with the MPX, though it may have been caused by user error. I’ll let you be the judge. I had a failure to load on the very first magazine on the MPX K. I inserted the magazine and pulled back on the charging handle, releasing it. I am aware that the MPX has a bolt release button, two in fact. But when I grab an unfamiliar firearm, I look for commonalities. While semi-automatic pistols can have their slide stop levers in different places (some don’t have them at all), they usually have slides which you can pull back on and release to chamber a round. In the same way, an AR and the MPX both have charging handle. But the difference is that the MPX charging handle has a very short stroke and that particular one needed the whole length to get into battery. It’s possible that I could have ridden the charging handle just enough to slow it down and prevent the bolt from going fully into battery. From then on I used the bolt release buttons to chamber the first round and encountered no additional failures on any subsequent magazines.

I’ve included two videos here. Both videos were filmed by Jim Grant of Guns.com and used by permission. If you’re still hungry for more MPX material, please check out his page:

http://www.guns.com/review/201...gun-supremacy-video/

The first clip will show various shooters, along with both versions of the MPX that were available to us that day.



The second, more detailed clip shows a modestly skilled shooter engaging an ISPC torso at 50 yards with multiple bursts and keeping those bursts on target (there is a different version of this video on DefenseReview.com that has better sound fidelity with regard to the multiple p-p-p-ing sound of the steel). The first two rounds are flat-out-misses (no ping from the steel). The second two singles are hits. What comes next is the most telling part of this string: even the most obnoxiously recoiling MG can get first round hits, but keeping entire bursts on target at 50 yards+ is where it’s at. And the MPX is capable of doing that even in the hands of, well, this guy:


Lefties: note forward ejection pattern.

The most accurate thing in this clip may be the shooter’s assessment of the MPX, rather than his accuracy with it.

Modus ex operandi, the MPX is a very comfortable and controllable platform. And why shouldn’t it be? It’s a big 9mm. Select fire MPXs are factory tuned for a 925-1200 cyclic rate, with the K model tending to run faster. And while the K did feel faster than the 8” there really wasn’t that much of a difference between the two, which is not the case with the MP5K vs an MP5A2 and in particular the Uzi vs Micro Uzi. I did not find it any more difficult to control the muzzle rise on the K than on the 8” model. What difference there was just required a little more attention to technique. You’ll also note that a lot of the shooters are using the K grip on both guns. On the MPX K, the lack of real estate on the handguard means you don’t have a lot of choice in the matter, but both guns got hot quick after multiple mag dumps.

In semi-auto I would consider the MPX to be a valid alternative home defense weapon to the shotgun, or even 16” rifle carbine. An 8” MPX with SB15 would be non-NFA (for the moment), shorter, lighter and lighter recoiling than both other options, accurate enough, and easy to reload, with enough inherent capacity to end the fight possibly without necessitating a reload at all. Fill it with very light, zippy 9mm rounds and you’ve pretty much got a gun that just about anyone, regardless of size or upper body strength, can use to put multiple rounds on multiple targets.

Some closing thoughts on the MPX: I will be getting at least one and Form 1’ing it or Form 2’ing it through my employer’s SOT and then transferring it. If you want one, but don’t like whatever bbl configuration it’s offered first in, I would consider just buying the available model and having fun with it, then buying the bbl configuration you want when it becomes available. If you want modularity, I would spring for the KeyMod handguard when it comes out. If you want light weight and heat resistance, consider upgrading to the carbon fiber handguard ($159-179). While the default aluminum handguard won’t cost you anything, it can get hot, though SIG could solve this problem by offering some type of non-metallic rail cover. I don’t know what default trigger it will come with, but if you know what AR compatible trigger you want already, get one and have it standing by. Fingers crossed that SIG will offer the Kate Moss option.

This little gun is going to change the pistol caliber carbine/pistol w/brace market. I think the best praise I can give to the MPX is that the MPX is going to be the gun that always goes with you to the range. It’s going to be the gun with which you teach new shooters how to handle a rifle. It’s going to be the gun that people line up behind you at the range to ask to put a couple rounds through. If you can have suppressors but don’t, it’s going to be the reason you buy one, and after that it’ll be your favorite non-22lr host, maybe your favorite, period. SIG plans for the MPX to be in their lineup for a long, long time. But more importantly, it can be in yours, starting this year.




<I have material for two more articles, but might have to take a break for little bit and deal with some “real life” issue I’ve been procrastinating on. I also have some questions out to SIG on the MPX and will update the forum with the answers I get back.>

This message has been edited. Last edited by: LDD,

Fantastic. Easily the most comprehensive report on the MPX on the internet.

That is an epic write up LDD.

Great write up LDD. This really makes me want an MPX

Thanks again, LDD!

There go my plans on a 9mm AR.

quote:

Originally posted by deadmanmike:
Great write up LDD. This really makes me want an MPX

But only in 357 Sig.

Very well versed and put together. Enjoyed reading it.

Nice. Looking at this closely.

Very interested

Saying I'm jealous would be like saying a T-rex is a big lizard. Excellent write up. Thank you.

Thank you for the excellent article. Sig needs to hurry up and take my money.

Excellent review, LDD. I really want one of these puppies.

Excellent write up! I want one of those soooooo very badly. I have come to th realization that SBRs are just plain fun.....arguably the most fun rifles to shoot period. This new MPX looks worlds better than my current 9mm AR15 SBR.

Damn you LDD! I don't need this, I don't need this, I don't need this.

A great write up, thank you! One question though, the magwell seems huge, and the mags, well, proportional. Is there a reason for that? Maybe it's just the lighting?

Hell yeah! Awesome!

Oat

This might give us an idea on price.

http://www.cabelas.com/product...E-PISTOL/1631337.uts

Guhhhhh. I need one today.

Wonderful write-up, LDD, with awesome detail. Greatly appreciated.

LDD, awesome write up.

One question, though. How does the monolithic upper rail interact with the multiple barrel/handguard lengths? You say that you can swap a receiver to any handguard and barrel config, but does that mean that the rail ain't full length on the longer models? If the different guns have different upper rails, is that going to be a problem? If you start with a carbine, and want to go to a 'k', do you have to chop it? If you start wih a 'k' and add longer barrel and hg, do you wind up with a gap up top? Is the upper rail somehow modular?