Sig 556 SBR Review

The Making of a Sig 556 SBR


An Exercise in Patience

By “Opie”

To start, I would like to state that this reflects my personal experience in acquiring/making a short barreled rifle. Please know your state laws in reference to the possession of National Firearms Act (NFA) weapons. Neither I or are giving legal advice and are not responsible for any misuse of the information presented.


Sig 556 SBR Review

For years I have known that it is legal to own a short barreled rifle (SBR) in my state. A short barrel rifle is defined as a rifle having a barrel shorter than sixteen inches. The provision in our state law states possession of an SBR is legal if the firearm is registered with the federal government. You can’t watch an action movie without seeing a very cool looking example of an SBR and having been a responsible gun owner for nearly twenty years I thought that might be a fun addition to my collection.

Also check out Opie’s M14 SOCOM II Photos here.

Sig 556 SBR Review

I looked at two different platforms to make an SBR out of. The first was the traditional AR-15. There are a ton of aftermarket parts and the possibility to changes calibers by switching out the upper receiver seemed like a good deal. I also found a “pistol” made by Sig Sauer. It was essentially a Sig 556 rifle, in 5.56mm, with a ten inch barrel and no buttstock. By definition, this was a “pistol.” I looked at pictures of Sig’s military rifles and really loved the look of them. Knowing that this project was going to be a hobby gun rather than a working gun I was inclined to give looks a lot more weight than I normally would. I also discovered that the Sig is a gas piston design meaning there would be no buffer tube sticking out the back of the receiver meaning the rifle could ultimately sport a folding stock – more on that later.

Once I bought the Sig 556 pistol, I began getting my paperwork in order to start the process of getting the SBR approved by the Bureau of Alcohol, Tobacco, Firearms and Explosives (ATF). There are different processes you can go through in acquiring/making an SBR. If you possess a firearm that you want to modify into a restricted weapon (short barrel rifle/shotgun) you become the maker of the firearm and are required to submit what is known as an “ATF Form 5320.1 Form 1- Application to Make and Register a Firearm” or simply a ‘Form 1.’  You need to print out this form so that both pages of the form are on one page (front and back). You will also need to have two passport photos taken. You will also need to have two completed fingerprint cards. Oh and you will also need a one time only payment of $200 payable to the Department of Justice. I then went to our local police auxiliary and had a very nice gentleman print out two completed FBI fingerprint cards. I completed my Form 1 while paying close attention to the instructions that are included with the form.

Sig 556 SBR Review

I then glued my photos to the back, stapled my completed fingerprint cards to the completed Form 1’s and then I took the forms to our local Sheriff’s department. The back of the form requires you to get the Chief Law Enforcement official for your jurisdiction to sign off on your application stating he or she doesn’t believe you are going to do anything nefarious with your NFA firearm and that the possession of it is legal in their jurisdiction. I would like to say that this was a very short part of the whole process but it wasn’t. I filled out an additional form at the Sheriff’s department with my biographical information. Approximately six weeks later my Form 1’s were mailed to me with our Sheriff’s signature on the back. I took my completed Form 1’s along with my $200 postal money order and sent off my packet to Martinsburg WV per the instructions. This is the part that I knew was going to take some time. From what I had read, I expected an approximately six month wait. It would prove to be just a bit longer.

Sig 556 SBR Review

A good portion of what I learned was taken from the internet by reading firearms forums and other resources. You must take care to ensure any information you act upon is properly referenced with federal law. That said, I learned before even starting my project that it is a bad idea to possess the buttstock you intend to put on your completed SBR until the ATF has completed you application and returned it to you. Legal jargon, mumbo jumbo, prison time, lose all your guns, meet bubba… Just wait until your completed and approved application is in hand.  I also learned that since I was going to be considered the maker of the SBR I would need to engrave my name, city and state on the receiver. After looking around, the company that kept popping up online for engraving was Orion Arms. I emailed the company and discussed what I wanted and they were quick to respond. While I waited for my Form 1 to come back I shipped off my receiver and had Orion do the engraving. It looks really great and I was impressed with the service I received from them.

Sig 556 SBR Review

I then kept waiting and waiting. If I could suggest one thing for this process it would be to forget that you have an application out. It falls in line with the old saying “a watched pot never boils.” I finally had forgotten about my application when I got an envelope from the ATF. Triumph!! Not so much. It seems that, even though my Sheriff said it was legal for me to possess a firearm I needed to fill out an additional form stating that I was a legal resident of the United States. I am pretty sure the form was “ATF Form 5330.20 – Certification of Compliance with 18 U.S.C. 9222(g)(5)(B).” I completed the enclosed form, faxed it back to my examiner and continued to wait. About three weeks later, one copy of my completed Form 1 was sent back to me bearing the coveted “tax stamp.” I now had the ok to put a buttstock on my pistol and make it into a rifle.

I looked at the different companies that offered folding stocks for the Sig 556 and settled on the ACE Ltd. push button folding stock mechanism paired with their SOCOM adjustable stock. This was one of the priciest options they offered but I liked the look of the stock and as I mentioned I was all about looks for this project.

Sig 556 SBR Review

I ordered the stock set and installed it on my pistol. That was it. Almost ten months of waiting and it came down to fifteen minutes of labor to “make” an SBR. People ask me if it was worth it. Yeah, absolutely. It’s satisfying to know you can legally possess something that is maybe a little unusual and not too many of your friends (unless you have exceptional friends) will have one.

What are my impressions of it? I love the Sig system. There are a lot of critics that say the US made Sigs have a lot of quality control issues. I haven’t had any issues with mine. The trigger is as smooth as you’d expect from a Sig. It doesn’t have the heavy gritty military trigger of a standard AR. The rifle is heavy for a 10” barreled gun but the ACE stock balances it out nicely. I have yet to have any misfeeds or malfunctions. If I had a gripe about the Sig, if you can call it a gripe, is that it throws brass way the heck away, easily fifteen yards of ejection. Plus the brass gets chewed up a little bit. While I’m not reloading 5.56 yet, the Sig’s brass would need a little extra work.

My ACE stock is super strong as billed. I love the fact that the stock can fold making the SBR a nice compact little package. One of the biggest gripes I had with the installation was the poor instructions. I eventually figured things out but I like Joe proof instructions. I am also still struggling with getting the folding mechanism to lock up when folded. A little oil has helped it lock up but it is a work in progress. I won’t fault ACE for that and in fairness I haven’t written them to ask about it. It isn’t a big enough deal to me.

Sig 556 SBR Review

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– Opie

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