SIG MCX Rattler BB Gun Review


Testers: Doug Wall, Stephen Archer

Caliber: .177 cal. BB

Model Number: AIR-RATTLER-BB

Test Date: Sept 28, 2023

Serial Numbers: 23E5512-0

Source of Supply: Supplied by SIG SAUER.

Condition: New.

We Like

VERY realistic.

That 3-shot burst!

Good shot count.


We Don't Like

Occasional BB jams in magazine.

Low Muzzle Velocity.

Not much else.


  • Value for Money
  • Comparison to Makers Claims:
  • Consistency
  • Appearance and Finish
  • Buying and Owning
  • Realism, Look & Feel
  • Realism, Trigger Action
  • Accuracy & Point of Aim
  • Shot Count
  • Muzzle Velocity



In the HAM Team’s opinion, the SIG MCX Rattler BB gun is the company’s best CO2-powered long gun yet!

It combines extremely realistic appearance and controls with good shot count and decent accuracy. It field strips, too, the price is fair and the warranty good. The three-shot burst capability is great fun, too!!!

The only real downside we found was an occasional, unpredictable tendency for BBs to jam in the magazine. (It’s the type of issue that could be just confined to this particular mag).

Overall, this is an excellent BB gun for plinking and for use as a trainer by owners of the firearm. It earns a HAM Gold Award for its combination of quality, usability, performance and value.


The SIG MCX Rattler BB gun is a very, very close reproduction of the SIG MCX Rattler SBR firearm. The main differences is that “our gun” uses a 12 Gram CO2 cartridge to power steel BBs downrange instead of 300 Blackout cartridges.

Oh, and at a Street Price of $169.99, it’s a cool $2,330.00 less than its powder-burning relation, which sells for $2,499.99! Plus, the BB gun offers a three-shot burst capability that’s not included in the civilian Rattler SBR firearm.

Price-wise, the Rattler is somewhere in the middle of the range for realistic, fast-firing BB long guns. Overall, that makes it very good value, particularly when we look at the performance of the gun tested by HAM.

SIG MCX Rattler BB Gun Review

SIG Sauer MCX Rattler CO2 BB Rifle 0.177



Overall, the SIG MCX Rattler BB gun is extremely realistic. Be VERY careful how you display this in any place where others can see you!

Size and appearance are very close to that of the firearm version. Only the weight is a little off. At 4 Lbs 9 Oz, it’s around one and a half Pounds lighter than the firearm version.

For the HAM Team, this is a far more realistic reproduction than the SIG pellet-firing, CO2-powered long guns. In particular we have, for the first time, a side-folding stock that is simply not possible with the design of the pellet-firing models.

As was covered in this earlier story, we couldn’t help accessorizing the test gun with an aftermarket AR-15 pistol grip, foregrip and red dot sight. These add-ons from Leapers fitted perfectly.

SIG MCX Rattler BB Gun Review

Another improvement compared to the pellet-shooters is that the SIG MCX Rattler BB gun has fully-functioning controls. Only the non-opening ejection port dust cover detracts from complete realism.

This Rattler also field-strips, just like a powder-burning AR. Again, this is a big improvement over the pellet-firing MCX models. We’ll cover the field-stripping in a subsequent story to give it full coverage.

There’s also mounting points for QD sling swivels. The rear mounting point (on the butt stock) worked just fine. However we could not get our QD sling swivels to stay engaged in the front mounting points on the hand guard. This was a shame, as we like fitting slings to our airguns!



The SIG MCX Rattler BB gun is supplied complete with synthetic, adjustable front and rear sights of the fold-down, “BUIS” type. The rear sight is adjustable for windage…

… while the front sight has an elevation-adjustment capability.

However we elected to fit a Leapers UTG red/green dot sight for testing.

Either way, the adjustable sights meant that we were able to set the point of aim to match the Point Of Impact without too much trouble.

As can be seen from the test targets, HAM Tester Doug Wall was able to achieve 10 shot groups of between 1 and 2 Inches CTC at 6 Yards. This is good accuracy for a BB gun and this continued out to 10 Yards, where the Rattler tested by HAM delivered “minute of soda can” accuracy.

Equally impressive was the accuracy achieved when in three-shot burst mode. The target below shows the results of no less than seven bursts fired into the same target at 6 Yards range.

As you can see, all 21 rounds impacted well inside the outline of a soda can. Doug was impressed with that!



The first thing most people ask about any airgun is “How fast does it shoot?” Well, Pyramyd Air shows a Muzzle Velocity of “up to 300 FPS”. But the gun’s box claims 325 FPS.

So HAM is taking the “box number” as our comparison point here.

The test gun shot at around 295 FPS in our relatively cool range at 68 degrees F. Based on testing with other CO2-powered air rifles, we would expect the muzzle velocity of the MCX to increase by about 2 FPS per degree Farenheit and to peak at a temperature approaching 95 degrees.

Factoring-in this increasing velocity with temperature, the Rattler BB gun tested by HAM would achieve the manufacturer’s “on the box” Muzzle Velocity of 325 FPS at a temperature of about 86 degrees F. That’s not unreasonable and makes the velocity claim a fair one.

The manufacturer claims that This selective-fire airgun “accurately replicates the feel and function of its 300 Blackout counterpart with outstanding attention to detail”.

The HAM Testers agree with this claim, too.



The SIG MCX Rattler BB gun tested by HAM delivered very consistent results.

Standard Deviation – the shot-to-shot variation of FPS in a string – was very well controlled at an average of just 6.50 FPS. This is a low value for a CO2-powered airgun and contributes to good on-target accuracy across multiple shots.

The trigger pull weight varied by just plus 8 or minus 4 Ounces about its 5 Lb 7 Oz average on test. That’s certainly a small enough variation to be imperceptible to the overwhelming majority of shooters, particularly for a fast-firing fun airgun that’s not a dedicated target rifle!



The SIG MCX Rattler BB gun has a very “solid’-feeling trigger. The trigger feels like a single-stage unit, there’s almost no take-up, so the gun fires immediately on a deliberate pull.

Again, the Rattler is not a sniper rifle, it’s designed for “close quarters government work” and the trigger of the BB gun reflects that.

SIG MCX Rattler BB Gun Review

Overall, the trigger and action of the Rattler BB gun is extremely realistic when compared to the firearm version. Obviously, SIG’s design control over both models is evident here!

Also there’s additional areas where the BB gun matches the firearm. For example, the safety cannot be set unless the gun is cocked. (Yes, it’s possible to force the safety lever into the safe position without cocking the gun, but it’s not intended to operate like that and is not recommended for long-term reliability!).

There’s an internal blowback mechanism built-in to the Rattler. This gives a feeling of recoil to aid realism. This – as usual – is more marked when the CO2 cartridge is full. Although not obvious to the user, there’s also a hop-up system similar to that found in airsoft guns.

In fact, the Rattler’s bolt actually strips the BB from the magazine and chambers it into the rear of the barrel for firing. This is different to the majority of AR-type BB guns, where the BB is fired directly from the magazine.

SIG MCX Rattler BB Gun Review

In addition, after the magazine runs empty, the bolt locks back. This requires a realistic reload sequence by either depressing the bolt release or cycling the charging handle to return the bolt to battery.

Yet more realism is provided by the three-shot burst fire system. This functions using a ratchet system, just like that in a powder-burning AR. This means that the ratchet advances after each shot, even in semi-auto mode.

The result is that – depending upon the position of the ratchet when burst fire is first selected – the first pull of the trigger may fire between one and three shots. This is exactly how a military AR functions.

So full marks to SIG for making the action of the Rattler BB gun as realistic as possible. That certainly makes it a great training tool for users of the centerfire version!



Unusually for an AR15-looking BB gun, the SIG Rattler is powered by just one 12 Gram CO2 cartridge. However, in spite of the energy-sapping blowback action, the Rattler tested by HAM delivered 90 shots from one CO2 cartridge before the Muzzle Velocity dropped to 200 FPS.

This is a good shot count for a CO2-powered gun with blowback. It’s certainly justification for the relatively low velocity and may be helped also by the hop-up feature of the action.



In the relatively cool HAM test range, at 68 degrees Fahrenheit, the SIG Rattler BB gun delivered an average Muzzle Velocity of 296 FPS across our standard range of test BBs.

This is low compared to other fast-firing BB long guns, however it’s definitely sufficient for the intended use of shredding paper targets and feral soda cans at ranges up to 10 Yards.

BBsAverage Muzzle VelocityAverage Muzzle EnergyAccuracy
Crosman Copperhead 5.13 Grain295 FPS0.99 Ft/LbsVery Good.
Umarex Steel 5.29 Grain289 FPS0.98 Ft/LbsExcellent.
ASG Blaster 5.32 Grain295 FPS1.03 Ft/LbsExcellent. Best Tested.
Hornady Black Diamond 5.36 Grain296 FPS1.04 Ft/LbsGood.
Daisy Avanti 5.44 Grain293 FPS1.04 Ft/LbsExcellent.



100 per cent. Plus!

Everything about the SIG Rattler BB gun shows beautiful workmanship and fine finish. With the exception of the non-opening ejection port dust cover, all the other controls and features of the centerfire version are functional and operate correctly.

SIG MCX Rattler BB Gun Review

The folding stock works as expected, with its side-pivoting action.

Once the stock is folded, the Rattler shrinks to a very compact 16 Inches in length, yet all the controls are accessible and the gun can be fired in this configuration.

SIG MCX Rattler BB Gun Review



The SIG Rattler BB gun is widely-available both online and in retail stores. So it’s easy to buy.

The warranty is for 6 months. This is longer than most other replica BB guns currently in the market.

SIG MCX Rattler BB Gun Review

In the HAM Team’s personal opinion, the minimalist pistol grip was somewhat too small for our hands. However, it could easily be replaced with an alternative AR-style grip, as we can see below.

Customization possibilities are enhanced by the M-Lok slots in the forend and top Picatinny rail. However, the flash hider is molded-on as a part of the barrel and so cannot be swapped for alternatives.

SIG MCX Rattler BB Gun Review

Magazine loading was easy. The BB follower is provided with a catch point that holds it back while BBs are being loaded. Also, the CO2 cartridge engagement screw is held captive inside the magazine (see photo above). This means that it cannot be lost and that a separate Allen (hex) key is not required to pierce the cartridge.

These are good things, as the availability of replacement/accessory magazines that are sold separately.

However, the test gun shot by HAM did exhibit occasional jamming and failure to feed in the magazine. This was seen with two of our standard test BBs: Crosman Copperheads and Hornady Black Diamonds and seemed to occur at random.

SIG pecialists suggest that a very small drop of silicon oil in the BB loading track may fix this issue. Alternatively – as with many replica BB guns – a replacement magazine can fix a multitude of potential issues as it combines BB-feeding, CO2 cartridge sealing and the operating valve all-in-one.

Finally a point that may – or may not – concern you. The SIG Rattler BB gun is supplied with a single-sheet “CO2 airgun safety guide”. In order to obtain an operator’s manual, you have to download it from the company website. All documentation is in English only.

SAFETY FIRST. As with all BB-firing airguns, it’s necessary to wear shooting glasses when firing this airgun. Also do not shoot at hard surfaces or water. BBs tend to bounce off these surfaces and may hit you, or something other than what you intended. If in doubt, don’t pull the trigger! Due to the realistic appearance of this product, handle it as you would a firearm. Do not display it in public or in any place where it could be mistaken for a cartridge firearm.



SIG MCX Rattler BB Gun Review




SIG MCX Rattler BB Gun Review

SIG Sauer MCX Rattler CO2 BB Rifle 0.177

This entire article including scoring, test targets etc is Copyright Hard Air Magazine and may NOT in part or in whole be reproduced in any electronic or printed medium without prior permission from the publisher.