Build Recipe 13 - Sig Rattler 5.56 SBR

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A compact SBR the size of a PCC PDW with the firepower of an AR15. 


This build is for packaging rifle-caliber stopping power into a pdw sized form factor that Is typically only seen in pistol caliber otherwise. A package this small is typically built for close range scenarios where the maneuverability of a shorter barrel is valued more than the long distance accuracy of a longer barrel. This setup also makes sense for scenarios where the gun must be stowed in a compact bag or compartment.

Why this one? 

Sig Sauer makes an excellent gas piston operating system that allows AR-like platforms to fold in half and fit into small packaging. Their gas piston operating system also allows for the gun to be fired while folded since there is no buffer or buffer tube in the stock. The Rattler is a proven platform that runs without malfunctions or headaches. It comes with an adjustable gas block which is nice for fine tuning the gas system when swapping between ammo types or when shooting suppressed vs unsuppressed.

Build Recipe 13 - Sig Rattler 5.56 SBR Build Recipe 13 - Sig Rattler 5.56 SBR

We stock these guns as pistols. They can be purchased and trasnferred as pistols without any need for a tax stamp since they are not an NFA item. If you prefer shooting the gun in SBR form with a stock, you can purchase a Form 1 Tax Stamp through us or anywhere else that will allow you to add a stock once approved.

Some things to know:

  • Any 5.56 gun with a barrel this short is going to be loud. A suppressor can be added to bring the sound down some, but if you are looking for a very-quiet gun that shoots rifle caliber rounds ask us about the 300 blackout version of this gun, which we also carry.
  • The smaller pistol grip that comes on the Rattlers is a love it or hate it type grip. If you are one of the people that hate it, I will put the Magpul MOE grip below in the parts list.
  • The photos show the gun in SBR form with a stock bolted on. You would need to purchase a Form 1 Tax Stamp to possess the gun in this configuration. We can help with that process if you are interested.


I went with a Sig Sauer Romeo4XT-PRO 1x red dot for this build because I like that the dimmer buttons are on top of the optic instead of the side, and it uses a commonly found battery that can be found in just about any junk drawer or TV remote in a pinch. This battery choice allows for a crazy-long run time of 50,000 hours. That's like 5 years if you kept it on the entire time. There are lots of optics that would work great in this recipe. I often use the EOTECH EXPS3-1 and the Holosun 510C in builds like this, but for this build I like the small and lightweight form factor of the Romeo4XT-PRO


I went with a JMAC Skeletonized Folding Stock Adapter with a Magpul SL-K stock on it. JMAC does make an even lower profile stock that has a fixed length but for this build I wanted to be able to set the stock to just the right length for my support hand placement and arm extension. This stock also allows for more surface area on your chin if that matters to you. 


I went with a Sig MLOK Vertical Front Grip on this build because the ergonomics feel more natural to me on guns with a barrel this short. I normally naturally c-clamp rifles but thats hard to do with a barrel this short so a vertical grip feels more natural in the wrist. 


I went with a Surefire M340C Mini Scout Light Pro for this build. Its 500 lumens of light in a very compact single-battery body, and it comes with all the mounting hardware you would need to mount it to a picatinny rail or an mlok slot and rotate it to where it feels best. I went with the picatinny mount off the top rail and rotated the light down to where it was close against the hand rail. Then I put the dual function switch where it would fit on the rail. The dual function switch allows you to press and hold for momentary activation or click and release for on/off. 


My go-to magazine for AR based platforms is the clear Lancer Warfighter mags. I like being able to see the capacity at a glance, and they've never given me any problems in use. 

Build Recipe 13 - Sig Rattler 5.56 SBR


If looking for a suitable case to carry this gun in, it fits perfectly in the Vertx 18" Bag.

Build Recipe 13 - Sig Rattler 5.56 SBR