The Ultimate Firearms Destination for the Gun Lifestyle


Photos by Straight 8

Our cover gun this issue was born from a miscommunication. Allegedly.

According to company lore, a SIG representative, on a business trip to the place where Great Britain used to be, was asked by a certain Army unit what the shortest-barrel option was for the MCX, as they wanted something small enough to fit inside the glovebox of a BMW, while still chambered in a rifle caliber. Due to a combination of jetlag, a strong British accent, and, no doubt, the Brit military propensity for attempting to drink everyone under the table, the rep believed his interlocutor to have referred to the 9mm MPX, which he said can indeed ship with a 4.5-inch tube in its most truncated form. “Alrighty then!” proclaimed our transatlantic brother. “We’ll take a bunch of them. Oh, and it’s your round.” It wasn’t until his return to New Hampshire that the misunderstanding was realized, but by that time the engineering team had already accepted the challenge of making the world’s smallest select fire rifle.

Now, the preceding account may or may not be true, but why let the truth stand in the way of a good story? We’ll let you be the judge of its likelihood, but there’s not much point in incurring the development costs involved in chopping down the already petite MCX, unless there’s a real operational need from a legit end user. Going from a 9-inch to a 5.5-inch barrel requires more than just busting out the angle grinder and hacksaw.


We attended the launch of the civilian version of the Rattler last year, but we’ve instituted an editorial policy that no gun from a major manufacturer will be evaluated until it’s in final production format. There are always problems in going from the limited run, handmade guns you’ll find at a media event to the version that ends up on the shelves of your local gun store. While we appreciate the opportunity to get hands on as early as possible, it’s unusual for there not to be changes made between first showing and retail. You’ll find coverage of new product launches at and RECOILtv, but we’ll reserve full reviews in print for the finished product.

In its current format, the Rattler is offered in two configurations, namely a factory SBR with folding stock and a pistol with a collapsible brace, both chambered in 300 Blackout. We requested the pistol version, as it’s transferable as a Title 1 firearm and can be carried across state lines without a, “Mother May I?” letter from the BATFE.

At last year’s launch event, SIG personnel indicated that the version spec’d across the pond would also be available, but thankfully, sanity has prevailed for the US market, and the 5.56 option is not currently cataloged. We can’t think of a practical application of a 5.5-inch barreled 5.56 gun, unless the idea is to simultaneously deafen your opponent while setting him on fire. Then again, we’ve run a 12-inch .308 in three-gun competition this year, so perhaps they’re onto something.


The Basics
The Rattler is a short-stroke, piston-driven semiauto, feeding from familiar STANAG-pattern box magazines. Designed to offer better ballistic performance than a submachine gun, but from a smaller package, it features a two-position gas regulator for use with a suppressor, full-length M1919 top rail, and free-floating handguard.

The MCX platform on which the Rattler is based went through some pretty significant changes last year in order to reach a 20,000 round service life, and the tiny rifle benefited from most of them. Taking cues from Knight’s Armament and their E3 bolt, the SIG part now has rounded, tapered lugs, rather than the original Stoner-pattern square numbers. This eliminates stress risers and largely prevents the familiar AR-15 failure point at the lugs closest to the extractor.  There’s an additional safety feature as well, in the form of a firing pin block actuated by the hammer, so if you’re in the habit of dropping your rifle muzzle down it’ll go clunk, rather than bang.

Another significant advance was the adoption of a two-stage trigger, which felt very much like the excellent Geissele SSA. Unfortunately, this has not been carried over to the Rattler. Our test gun has one of the worst GI-style bang switches we’ve encountered in the past few years; gritty, notchy, and breaking at around 9 pounds. It’s a real letdown on a gun that’s supposed to retail for almost 3 grand.

The Rattler does, however, retain its parent’s anti-wear features, such as replaceable, hardened steel cam track reinforcement and feed ramps, as well as steel pins where the charging handle latches make contact on the upper receiver. The barrel is replaceable at the user level, retained by two Torx-headed cross bolts. Compared to an AR-15, there’s a definite feeling of solidity and longevity to the MCX upper, like it’s designed to last a couple of lifetime’s worth of hard use. Which it should, given the price difference.


For the rest of this article, subscribe here: RECOIL Issue 37

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