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Random thoughts on the SIG Rattler

I traded off my SIG Rattler in .30 Short & Weak. The new owner should be receiving it today so I thought I should get around to writing down my thoughts on the gun.


It wasn’t really an impulse buy when I got it. Instead of impulse buying things, what I tend to do is dwell on the idea of an item for a while, sometimes years, putting the concept on the pedestal until I buy it, only to then think, “Why did I get this?”.

Mind you, I like the Rattler. I loved how it handled and I love the form factor, but there were plenty of things I didn’t like.

But first, what is a Rattler? SIG made a gun mixing features from the SIG 55X line of guns and the AR15. This lead to the MCX line of guns. They have had something like 2 or 3 generations of these guns, and they have been very popular and successful. A military group then requested a kit to modify their M4 carbines to a very short barrel and compact package. The MCX is capable of using their properitary lower, or an AR15 lower with adapter, so SIG made a custom version of the MCX rifle for this customer. This shorter custom gun was then sold to the public as the Rattler.

The Rattler is available in 5.56×45 or .300AAC. You can get it as a pistol or a short barreled rifle. There is also a model with a longer handguard and tan finish for suppressor use called the Canebrake.

Yup, you read that right, a 5.5 inch barrel. Hence the name Rattler, like tooth rattler.

I haven’t fired the 5.56 version, but I didn’t think the muzzle blast on the .300 was bad at all.

I love the idea of a small folding carbine. Something that easily fits in a backpack or other small space, but is still high capacity and capable of defeating body armor. A gun like this with a brace or stock is far easier to shoot to longer distances than a pistol.

I could ramble on more, but let us look at the gun instead. I liked the Rattler, but I would critique a few things.

Companies are always looking for ways to cut costs. Many newer gun designs have receivers that are aluminum extrusions to reduce cost. On the MCX they went with a 6061 aluminum receiver and used roll pins or metal inserts to function as wear points. I read that on the Rattler 7075 is used. I wonder if the change was due to customer (read military) requirements.

Note the spiral roll pins where the charging handle latches too.

The charging handle is ambidextrous out of the box. That is a nice upgrade. But it is a little small. While certainly functional I would have preferred slightly larger latches. There are already aftermarket charging handles with larger latches. This isn’t a complaint of mine but just a comment.

What I would complain about would be the lower. For a next generation weapon system, why isn’t it fully ambidextrous?

Personally, if I were to do it again, I would get a fully ambidextrous AR15 lower and run a Rattler conversion kit on it. That way I would have a bolt latch on the right side, and a nicer mag release on the other. SIG uses a (for lack of a better term) Troy style left side mag release. I find this stiffer and harder to use than the Norgon or KAC style left side mag releases. Not hard or bad, just not as nice as the others. The LMT ambi-lower will not work due to the right side bolt catch interfering with the profile of the Rattler upper.

Their firing pin safety seems like a last minute lawyer driven add on. It makes disassembling the bolt carrier group a little more difficult.

The Rattler was purpose built for its’ size. Due to that it loses a fair bit of the modularity of the rest of the MCX line. You can not use the same hand guards as the rest of the line do to a change in the length of the upper. The piston system is different so if you want to use a non-Rattler barrel you have to swap out some of the operation system. This makes barrel and caliber changes even more expensive. For example, a 5.56 barrel for the .300 Rattler is about $550. It is recommend you then buy the 5.56 handguard which is slightly different length than the .300 hand guard. At these prices, you could build a couple of short AR15s and have cash left over. But, to be fair, this can be said about most high end competition of the AR15.

I find it a little silly that they built an accu-wedge into the design of the gun. When removed, there was a fair bit of movement between the upper and lower. With it in there normally removing the take down pins was very hard with out tools.

What did I like about the Rattler? Aside from the compact size, AR15 manual of arms and ergonomics, etc.

I like the barrel system. A clamp with 2 screws holds the barrel in place allowing for the barrel to easily be removed for caliber changes or deep cleaning. I like how the handguard is held in place by the forward take down pin. It makes cleaning the weapon after inclement conditions so much easier. The Rattler appears to be “Over The Beach” ready.


An aside:
It seems to me that there are different personalities of gun owner.
Some buy a gun and never mess with it.
Some will make small changes, to personalize or modify a gun to suit them better.
Others have to tinker, do it them selves, upgrade and modify. If they can’t personalize or heavily modify a gun they don’t want it.
The Rattler might be less ideal for that last group as there is less modifications available to it. But that hasn’t stopped some.


Ultimately what got me to trade off my Rattler was the cartridge. I’m not a fan of .300 blackout to begin with and the shooting I did with it gave me to reason to like it.

I never got what I would consider a good group out of the Rattler. Longest range I shot it at was 25 yards and I would only about 2 inch groups at that distance. I felt that was pretty awful. Mind you, shooting was only ever done with iron sights or red dots and I only tried a couple types of ammunition. The gun may have been capable of better, but other than checking that the barrel was installed properly, I never tried to sort out why it was performing so poorly. But I can easily shoot any of my ARs far far better, even with iron sights. That accuracy was a fair bit of a disappointment.

The Rattler fits in a similar niche to the submachine gun. It is not built for longer range shooting, and with the short barrel ballistic trajectories are pretty bad. I read that the gun was designed for use with super sonic ammunition for terminal effectiveness, but it is pretty fun to shoot suppressed with subsonic ammunition.

But for me, I don’t reload .300 and I didn’t want to spend the money on hundreds of rounds for training. I thought about buying a 5.56 conversion barrel so I could shoot it more, but that would have run me something like $550-600 dollars. I kinda balked at that idea as I wasn’t sure if I’d rather shoot $600 worth of .300 or would rather have the ability to train with 5.56. Finally I got the B&T APC9K which fit my desires for a compact short range gun, so I decided I’d trade off the Rattler for something I’d use more.

I am also spoiled by the self regulating gas system on the AR15. I love being able to just put on or take off a silencer with out having to change anything. On the Rattler I had to adjust the piston system depending on if I was shooting sub sonic or super sonic ammunition, or if I was shooting suppressed or not. Using the wrong setting could cause it to fail. Just annoying to deal with. I see proponents of .30 short and weak claim how no other guns can have the capability to switch between super sonic and sub sonic ammunition in the same mag and have this great variety of capabilities, then in the same discussion I read of people having to have different buffers and springs for their .300 AR15 for different loads. It just doesn’t seem right to me to have to fool around with the gas or recoil system of what might be a fighting firearm just because you changed ammunition.

It is a cool gun, and I don’t think it is a bad gun. It just wasn’t right for me. I’m not really interested in a 5.5 inch barreled 5.56, and I’m not interested in a .300 blackout, so I decided not to keep it.

Oh, and some of the sub sonic ammunition would leave lots of unburnt powder in the lower. That always seemed odd to me.

A few misc photos:

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