SIG 556 Patrol conversion to SBR?

[HauptmannAmerika]

I have recently fallen in love with SIG rifles and wish to add a 556 SBR to my collection. However, I don't want to buy a factory-built SBR (552-style) from a dealer. I've seen a lot of posts on this and various other forums about converting a 556 pistol to an SBR, but none about converting a 556 Patrol rifle to an SBR. The way I figure it, I have a few different options when I buy the rifle:

1) Chop the barrel down to whatever length after I've gotten the stamp back from the ATF.

2) Find another (shorter) barrel and have a gunsmith drop it in.

or

3) Buy a pistol and simply swap the uppers.

Problems I see with these ideas are as follows (respectively):

1) I probably will have problems having the end of the barrel re-threaded, as the SIG barrels flare out on the end to accommodate standard A2 flash hiders.

2) I have not been able to find any vendor that sells short SIG barrels and I'm not sure that anyone even makes them.

and

3) I read somewhere that SIG puts their serial numbers on the upper receiver rather than the lower (this is the case for my SIG 522), so the swap would most likely not be possible if that's the case.

So, what I'm asking is...

Which one of these choices is the most viable (not necessarily the cheapest, but cheap would be nice) option? Or is there another that I've missed?

Keep in mind...

The reason I don't necessarily want to get the 556 pistol and convert it is that I want the SIG lower receiver with the SIG folding stock, not a buffer tube and AR-style one.

Any and all advice is greatly appreciated!

Thanks,
Gabe

P.S. Does anyone know if the lower receiver from a SIG 522 is the same as one from a 556 rifle? I assume the trigger assembly is somewhat different, but if it's not, that's good news.

 

[MasterSergeantA]

Cap,

The upper is the serialized part of the SIG. I bought a SIG 556 pistol and then picked up a carbine lower on another of the gun boards to build my SBR. It is the standard SIG folder. I was also able to remove the rear plug on the pistol lower and install a folding AR stock quite easily. So I have my choice of which one to run. I think the 'extra' lower ran me about $350...cheap compared to some mods.

So #3 is probably the most viable.

Cutting the barrel (#1) would probably involve installing a short sleeve to bring the barrel diameter up to the right size. There are a number of good smiths who might do this. Probably no more that $200 to get the work done.

Methinks that SIG would be the only viable source for a short barrel (#2), but they might not be willing to sell you one. If they would, you would probably have to ship them the upper and a copy of the Form 1 to have the barrrel installed. Just a guess. They 'should' have the pistol barrels...since they make the pistols. *shrug* But dealing with the manufacturers can be a special kind of hell. They might even sell the lower to you if you ask nicely, but again they will probably require you to provide proof that you are permitted to 'make' the SBR.

I do not believe that the lowers on the 556 and 522 are 'swappable', but I can pull both of mine and check. The dimensions are likely to be the same, but I am thinking that a lesser grade of plastic might be used for the 'toy' gun.

 

[gggplaya]

Adco wll shorten your barrel and install a muzzle brake for $200. Here's the link, like 7 items down.
http://www.adcofirearms.com/shopservices/shop_.cfm?code=1

 

[HauptmannAmerika]

MSG,
Thanks for the advice! I agree about #2 -- dealing with manufacturers is never pleasant. I'm still on the fence between #1 and #3, but I'll definitely take everything you said into consideration!

gggplaya,
Thanks for the link! I'll check it out.

Whatever I decide to do, I'll post updates and pictures when it's that time.

 

[MasterSergeantA]

http://www.sturmgewehr.com/webBBS/parts.cgi?read=297669

 

[kimberkid]

I went the pistol-SBR route back in '08, originally I unscrewed the plug from the back of the receiver, got a hinge kit from ACE and magpul CTR stock but recently I picked up a Classic receiver on Gunbroker and a swiss stock as I don't care for the adjustable folder that came on it ... compared to prices now I've got way too much in this gun but on the upside I've had it for a little over 3 years ... it is my favorite. Note the McDonalds toys I shot at 100yds with 62grain Silver Bear; its more accurate than my 556 carbine.

​

The 556 and 522 lowers are not interchangeable.

If you cut down the barrel, you will likely have to enlarge the gas port slightly for reliable cycling but it does sound like the most cost effecient way to go.

BTW - did you notice on Gunbroker a dealer is selling the P522-swat for $299 ... I picked up one and am now waiting on a stamp for it.

 

[HauptmannAmerika]

MSG,
Firstly, thanks for the link! Secondly, I've decided to go against the grain and do #1. I picked up a 556 Patrol (standard model) for $1089 new from a local shop. I then picked up a Trijicon Reflex sight (6.5 MOA dual illuminated - Fiber optics + Tritium) from Amazon new for $460. I sighted it in the other day and I am in love! I already sent off the Form 1, so I should hear back by January some time, hopefully. I'm sure the chrome will take a little beating when the gunsmith chops the barrel down, but I don't think it'll affect the accuracy of the weapon too much. I'll publish my test results once everything's done.

kimberkid,
Thanks for the comments/advice! That's a nice setup you've got there! The McDonalds toys are a nice touch, LOL... Out of curiosity, why would the weapon have problems cycling if the barrel is cut down? The gas tube/piston assembly is the same size as a 556 Pistol... but admittedly, I don't know that much about piston assemblies. Anyway, thanks again for the comments -- my love affair with SIGs has only begun!

P.S. Sorry it took me so long to get back to you guys -- my work has recently become quite demanding/time-intensive...
P.P.S. Here's a picture of my current setup:

P.P.P.S. Could you please let me know if the picture showed up or not? If not, could you let me know how to post a pic?

 

[Sam Cade]

. Out of curiosity, why would the weapon have problems cycling if the barrel is cut down? The gas tube/piston assembly is the same size as a 556 Pistol... but admittedly, I don't know that much about piston assemblies.

In general shorter barrels require larger gas ports to function since the gas is in the system for a shorter period of time.

 

[MasterSergeantA]

kimberkid...what sights are you running on your SBR?

 

[Mudinyeri]

Shortest, cheapest, easiest route to a SIG SBR:

1. Buy SIG P556.
2. Apply for stamp.
3. Wait forever.
4. Receive stamp.
5. Engrave receiver.
6. Add stock.
7. Fire when ready.

 

[kimberkid]

MI front and GG&G BUIS in the back

 

[MasterSergeantA]

Cap,

I think you have to 'host' the photos on a website like photobucket and link them to the post. Your photo did NOT show up because we cannot see your hard drive (a good thing, most of the time) and that is the link you provided. It should ONLY work from your own computer.

I can look around to see if there are instructions on the site, but kimberkid obviously knows how. Perhaps he will educate us both.

 

[kimberkid]

Cap,

I think you have to 'host' the photos on a website like photobucket and link them to the post. Your photo did NOT show up because we cannot see your hard drive (a good thing, most of the time) and that is the link you provided. It should ONLY work from your own computer.

I can look around to see if there are instructions on the site, but kimberkid obviously knows how. Perhaps he will educate us both.

MastersergeantA has it exactly right ...
You have to host your pictures to an on-line server that is always up; and photobucket is one of the easiest to use plus they have free accounts so you can try it out ... but anyway you upload your picture then copy the link and past it into your post wherever you want the pic to appear.

 

[wally]

Doesn't THR have photo hosting built into the forum? Check out "manage attachments" under your forum "User Control Panel".

That is what I always use. Photobucket comes and goes, lots of broken links there in older threads found by searching.

When posting photos make sure the jpg EXIF info has nothing in it that can come back to haunt you -- a lot of new cameras have GPS and write image location co-ordinates to the EXIF data. That and GoogleEarth could lead a thief straight to your door

 

[kimberkid]

Doesn't THR have photo hosting built into the forum? Check out "manage attachments" under your forum "User Control Panel".

That is what I always use. Photobucket comes and goes, lots of broken links there in older threads found by searching.

When posting photos make sure the jpg EXIF info has nothing in it that can come back to haunt you -- a lot of new cameras have GPS and write image location co-ordinates to the EXIF data. That and GoogleEarth could lead a thief straight to your door

Maybe I'm blind ... and that probably the case.

I go to the User Control Panal, at the bottom I see Miscellaneous and sub-catagory Attachments, but when I click on Attachments it says I have no attachments and I don't see any where to manage my attachments ...

 

[wally]

I'm sorry, I mis-stated a bit, the manage attachments is a button on the bottom of the screen under "Additional Options" when you are composing is "Advanced" mode.

I'm not surprised the user control panel doesn't show anything if you not yet uploaded any images.

You have to have scripting enabled for the advanced mode to work.

 

[MasterSergeantA]

I can get into the "Go Advanced" tab, but where do I upload images?

 

[Sam Cade]

I can get into the "Go Advanced" tab, but where do I upload images?

You can either click the "insert images" toolbar button to paste in a link or hit "manage attachments" below the text box to append a file (which can be an image) to your post

 

[kimberkid]

Ah HA!

 

[RAINS]

Would not go the Patrol route for two reasons. Sig of recent is so/so on QC and chopping the barrel will for sure void the warranty. Second when I looked at having it done you could not easily change the mussel device on your newly chopped barrel. You were stuck with one. Still it is by far the cheapest but also riskiest way. If you want the factory stock anyway. I hope it works out for you.
I was in your shoes a wile back. Then the skies opened, the light of heaven shined down on me and I found a NIB factory sig 556 SBR for $1150 shipped. Even with my dealer's transfer fee I'm only in it $1200 before ATF fees. Did I mention the sig lifetime warranty on it?
A side note. "YES" my credit card did break the "sound barrier" coming out of my wallet to pay for that factory sig sbr. Now if uncle sam would get off his ass maybe I could actually shoot the dammed thing! I live in a free state. I'm not used to this waiting crap for guns!

 

[kimberkid]

Actually this would be cheaper than paying someone to cut down you patrol barrel ... sell your pistol lower on Gunbroker and you'll get pretty close to what you can buy a classic side-folder lower for (and if you have an AR stock laying around put it on your pistol lower for wider appeal)

Since its not a serialized part it makes no difference!

 

[HauptmannAmerika]

Okay, after much ridiculousness, here it is! Thanks for the help everyone!

P.S. Thanks for the heads up on the metadata Wally -- I fortunately have a camera new enough to take good pictures, but old enough not to have GPS on it! As for thieves, I have only this to say: I pity the fool.

 

[MasterSergeantA]

So now do you cut the barrel?

 

[HauptmannAmerika]

As soon as the stamp gets here, yup. Should be about January or so I'm guessing... As far as further modifications are concerned, I don't think I'm going to do anything short of removing the front sight. I've got a SIG 556R on order which will be my next project. I'll post a new thread once I get it.

P.S. KimberKid -- What's the make of that magazine you've got in your rifle? And do you like it? I've found that PMAGs work like a champ with mine.

 

[HauptmannAmerika]

Here are a couple of fun photos related to my rifle:

Shot Group from sighting it in:


Damage it did to my lawn: