SBS Technical Info Thread

[Raoul_Duke 113]

12" with long Tromix handguard.

 

[rotortuner 0]

Thats a good looking, well proportioned gun.

 

CJG

[justinmcmillion 77]

12" with long Tromix handguard.

 

 

I too want to build a 12" (just looks right) plus I don't think I have the skill to do an 8"

 

I was wondering if the hand guard above is for sale? If not what other options do I have? How do some of you shorten the gas tube on the 12". From this picture it seems an entirely new one was made. To me it looks as thought the tube is tac welded in the rear sight block, I was wondering if it was possible to cut the tube off and grind out whats left of it in the sight block then cut tube to proper length and slide it back in and either weld or epoxy it in?

 

Also on the gas piston, I was thinking of drilling out the places where the crimped in the threads unscrewing the gas piston and making a new one on the lathe (using stainless), then pining it back after threading it in. Would this be a proper route to go?

 

I am turning the bbl down to move the gas block rearward 2" re-welding old gas ports and drilling new ones, cutting bbl to 15.5" or 16" rethreading and permanently attaching my flash hider (attain 18" total) until the paper work returns, then chopping the bbl to 12.

 

Thanks in advance for any information.

[justinmcmillion 77]

I just finished my project and everything worked above except the gas tube. I now see why tony makes new ones. It is possibly to use the factory gas tube as you will see in my pics but be prepared for some modding.

 

I made an entirely new piston to replace the factory one and pinned it in place.

 

Overall the project went well but its more in depth than one might think.

 

If anyone would like detailed info or more pictures just ask. (maybe here so others might benefit?)

 

BTW i love the look of the gun, its just right IMO

 

 

 

[motoguy 1]

If anyone would like detailed info or more pictures just ask. (maybe here so others might benefit?)

 

BTW i love the look of the gun, its just right IMO

 

 

 

 

Looks great! I would love for you to share as much info as you feel comfortable with. Pictures, process, reasoning, etc.

[justinmcmillion 77]

Looks great! I would love for you to share as much info as you feel comfortable with. Pictures, process, reasoning, etc.

 

motoguy,

 

Thanks, I'm hoping to do a full write up on it, but finding the time is the problem, here's the short and simple, and probably all I'll write, but feel free to ask questions, and Ill answer to the best of my ability. I wont explain the stuff that you can find easily on here just the technical details of the overall shortening, so if you wanna know how to take the gas block off read the forums.. Hope that doesn't sound rude and I don't mind one bit to explain this to any one, but every bit of dis-assembly information you need is on this forum, that's where I got it.

 

Another thing before I go any further, if you don't have access to a lathe then I wouldn't even consider attempting this project.

 

Original purpose: Move the gas system 2" rearward and cut the bbl to 12" (based on Tony's findings) for a CQB shotgun - smaller lighter and faster on target.

 

Because NFA stamps aren't overnighted and free I decided to try this before applying for the stamp (all except cutting the bbl to 12" of course)

 

*I feel it necessary to say... "All NFA rules apply"

 

First was dis-assembly; (normal breakdown of the gun) + drive pins out of gas block, drive gas block off remove gas tube, next was removing the bbl which at first provided to be a pain, but eventually I turned a piece of brass the exact specs of a 12g shell and used that to drive the bbl out after driving out the pin and heating it. A propane torch will work but the bbl will not move unless you heat the receiver.

 

Below is a picture of the brass 12g shell clone in place

 

 

After we drove the bbl out we then measure 2" back and put the bbl in the lathe and turned the bbl so the gas block would slide 2" back. We then welded the holes from the original gas ports and pins that held the gas block in place, put it back in the lathe and turned it down to a smooth taper that blended into the original bbl taper. We also cut the bbl down and re threaded so that with the flash hider it would be 18 1/8".

 

Next was the fun part of shortening the gas tube. We really went out of our way on this and it took a good while to do it. We chucked the tube in the lathe and cut the tube from the inside out until the rear part that houses the rear sight was no longer attached. Cut the amount needed off and mocked it up. This is where we ran into a problem... The bolt carrier's O.D. is larger that the smaller fluted section of the gas tubes I.D. which is pretty much all that was left.. So we decided to expand the gas tube in order to allow the carrier to pass. I liked the fluted look and was prepared to make a gas tube, but it all worked out and I'm very happy with it.

 

 

After expanding we slid the tube back into the rear sight housing and got everything ready to mount the gas block. (Re Installed the bbl) After driving the gas block on the tube was pressed into the rear sight housing so tight I didn't feel that it needed any other means of attachment, considering it cant come out unless the gas block is removed. We eventually had to slightly shape the bolt carrier as you will see in following pictures to allow for smooth operation. We then drilled the holes for the gas block to pin it into place, and drilled the gas ports (drilling the gas ports can be a pain, its best to make a jig and do it that way. Drilling on a round surface at an angle is no easy task esp with the size bit you have to use. I would get advice on how to do this from someone else (I'm just glad no one can see my ports )

 

Next was the "piston" we decided that it would be easier to just make a new one rather than modifying the original. The original is threaded then for lack of better terms squeezed at 2 tiny pressure points that lock it in place, simply drill those out down to the piston but not all the way through and the piston threads out.

 

 

We then did all the proper measurements and made a piston to replace the original. After we got it just right we drilled it all the way through for a roll pin.

 

 

You can see in this picture below the very slight modification I made to the carrier by turning it down a tiny bit on the lathe so there was no clearance issues.

 

 

Sorry for the dirty carrier/"piston", I just ran 300rds through this this to see how everything went and didn't clean it yet.

 

This picture shows the part of the tube I removed (minus what was inside the rear sight mount), how much bbl i cut off, the original "piston" the Brass knocker and of course the new carrier/piston.

 

 

Comparison...

 

 

Last step was to permanently attach the Flash Hider to meet NFA regulations. And install HG which I just drilled a hole in the bottom added a rail and fg, and cut the sides down for looks.

 

Finished Product (until LRBHO and bolt release are available, or I get a wild hair)

 

 

It Runs GREAT!!!! Cycles low brass on 3 and 2 of the gas fixxr plug so the system is a tad over-gassed but it beats under gassed any day!

Im still debating applying for the stamp, I realized that I really enjoy the boosted reliability of the gas system and think I might just keep it the way it is and save the stamp for a 8" S12

 

Thanks for reading this and I hope this helps someone.

 

Justin

[barefootH2O 1]

Thanks for the write up. Unbelievably well done. if this post described a fiero conversion I would be driving a ferrari right now. At -10 as it is in MN as I write this, it would suck..... my saiga shoots at these temps.! my neighbors think I'm nuts.

[justinmcmillion 77]

Thanks for the write up. Unbelievably well done. if this post described a fiero conversion I would be driving a ferrari right now. At -10 as it is in MN as I write this, it would suck..... my saiga shoots at these temps.! my neighbors think I'm nuts.

 

No problem Hope it helps

[Steppe Sweeper 22]

Seriously excellent thread, hard earned knowledge getting shared. SBS is N/A here, gets you a long stay at the ol' Buttfuck Hotel. Nice to understand all the complications involved with a short tube on a self shucker. There are some serious masters of gun design on here. Mikhael K. himself would learn a lot on this site. And in my mind Tony is up there with JMB and Hymie Lebman. Seriously great stuff guys, thanks for this thread.

 

Anybody run a 20 gauge? First Saiga I ever heard about was an article by Leroy Thompson on guns of Russian OMON. It was a 20 (IIRC shorter than the Izhmash S-20K EXP01 looked no longer than 12"), all stock except had a Bulgarian triangle side folder on. Went on to say these guys see shotguns as doorbusters near exclusive, but when they play '9 hole' on a Vor soldier, it's usually a personally owned Benelli. But I was smitten with that SBS 20 ga. Right there, ultimate evolution of coach gun, a modern 'Auto & Burglar'(not what Taurus tries to promote the Judge as), Clyde's wet dream. Since then yeah, the Tromix S-17 is there to make our mouths water, the POS 'Accelerator', other little AK Alley Kleaners. Still, something about a short barrel 20 seems so much more practical and useable, something more weapon for fighting than fantasy brought to life, but most likely for range use and adulation. Would definately do the job, but who likes going to war with a 11 oz. .357 Mag?

 

I think a 10", (or 8-12")folder KISS S-20 would make a hell of a SD/HD cannon. Maybe the best to be had if trustworthy enough. 5 shot in the carry folded position, couple 8's ready to go if something goes real ugly; maybe on some kind of little PDW harness if you were watching a VIPs back in public or running the limo, deploy just like a 74U/Micro Galil/HK-53 type subcarbine or a PDW would be. That's a weapon to restore opinion of the combat shotgun in CQB. Tell me about the SBS 20, interesting to read some specs for little sister. Can never have enough info available.

 

I would've thought there would be special pucks made for these. Also, as far as reliability goes. With a load it takes smooth and spits out the shell, clean gun, etc., do they 'limp wrist'?I saw the video of an AOW pretty much bump firing, but that's not a whole story. Autos(all operation types) have gotten to where you can dump a tube full of dove loads one handed upside down, but with the mechanics and all can a snub nose Saiga? The timing issues from standard brakes, or feeding from a drum? Lot of things going on, in their own time and space, never like precision clockwork...

[mike12345 18]

I'll put in my .02 here.

 

For those of you interested in shooting only Highbrass, buckshot/slugs...

 

I opened my gas ports on my 11in barrel from .073 to .082 Drilled on an angle backwards. It cycles fine on setting 1 with all highbrass ammunition or with a gunfixer gas plug screwed all the way in. (never tried birdshot)

 

I would advise you start off with a smaller gas port size and work your way up. It may be a pain in the ass but the smaller these holes need to be, the better off you'll be. The less recoil you'll feel when the bolt dosent SLAM into the rear trunion. You'll avoid getting trigger slap from the bolt throwing the hammer back so hard, the trigger slaps your finger. (I have shot saigas that have trigger slap, it sucks) You'll also get less fowling in the gas block.

 

If you drill too small, you can always drill again. Having to weld up holes and re-drill I woulden't even want to try.

 

 

I dont see a point to birdshot in a SBS/combat shotgun, or making the gasports larger for it to cycle with birdshot, that results in a overgassed gun. Train as you fight and all that.

Edited February 20, 2010 by mike123456

[BobAsh 582]

I dont see a point to birdshot in a SBS/combat shotgun, or making the gasports larger for it to cycle with birdshot, that results in a overgassed gun. Train as you fight and all that.

 

My SBS has nothing to do with self-defense or combat, and I want it to be able to shoot anything/

[inflightmissiletech 27]

Is anyone aware of where to get the pins that hold the barrel in place?

And further on the subject...I believe that if i put a had grip on the weapon it becomes a DD especially if the magazine rotates. That is just my interpretation of ATF website. So if I plan on legality and application and such to the $200 tax stamp I had better put on the same app that the barrel is shortened etc. Is it easier for a 12+ inch barrel to just add and enlarge gas ports or would fine tuning that system make it worth while to move the gas block?

I have access to a machine shop so milling a new piston and drilling the new ports and turning the barrel will only cost me a couple cases of beer but i will have to do all the work, and i'm a horrible welder and would be very embarrassed of my welds popped out at the range and vented the barrel at that angle back at my hands or face.

[BobAsh 582]

It's not a DD no matter what "grip" you put on.

[inflightmissiletech 27]

whatever I don't mean to pirate your thread I thought the question was relevant. Edited March 1, 2010 by inflightmissiletech

[inflightmissiletech 27]

Is it easier for a 12+ inch barrel to just add and enlarge gas ports or would fine tuning that system make it worth while to move the gas block?

Edited March 1, 2010 by inflightmissiletech

[03psd 0]

unbelievably awesome information in this thread, especially for a Noob. No doubt saved dozens of dumb repetitious questions. I do have a couple not answered in the thread thus far.

 

I see lots of 8" and 12" guns but very little in between. Why?

I an wanting to go 10" plus a muzzle device. I think the 8" is a bit short and the 12" a bit long.

 

I have done the trigger conversion to my S12 with Cobra parts. It went very smoothly, however I am not comfortable doing the shortening and gas work. Who do I need to sent this off to have it done right? also it would seem I need tohave my Form 1 approved prior to shipping it off, or certainly receiving it back. Correct??

[BobAsh 582]

whatever I don't mean to pirate your thread I thought the question was relevant.

 

It's a relevant question, but you can't make an S12 a DD no matter what you do to it. BATF would have to name the gun specifically.

Edited May 10, 2010 by BobAsh

[BobAsh 582]

Is it easier for a 12+ inch barrel to just add and enlarge gas ports or would fine tuning that system make it worth while to move the gas block?

 

Easier, for sure. It would have pretty big ports though, so it would foul faster and/or not run birdshot.

 

Tromix moves the gas block back on all SBS's because this achieves the maximum reliability with maximum ammo capability; better than some factory guns actually.

[BobAsh 582]

I see lots of 8" and 12" guns but very little in between. Why?

 

Mainly because those are the sizes that Tromix offers and Tony is by far the top maker of SBS Saigas, so most other guys have used the same model.

 

Tony has made a few 10" guns, and they work great. You can make any size you want, really. He just standardized on those since otherwise guys would start ordering 14.625" barrels if you didn't.

 

I have done the trigger conversion to my S12 with Cobra parts. It went very smoothly, however I am not comfortable doing the shortening and gas work. Who do I need to sent this off to have it done right? also it would seem I need tohave my Form 1 approved prior to shipping it off, or certainly receiving it back. Correct??

 

Obviously Tromix is the best answer for an SBS. Tony has built thousands of short-barrelled Saiga shotguns.

 

Form 1 if you are doing the job yourself, Form 4 if you are having it done. Either way you MUST have the paperwork in hand before you can possess a sub-18" gun or you will commit a felony.

Edited May 10, 2010 by BobAsh

[joelrod47 373]

I see lots of 8" and 12" guns but very little in between. Why?

 

Mainly because those are the sizes that Tromix offers and Tony is by far the top maker of SBS Saigas, so most other guys have used the same model.

 

Tony has made a few 10" guns, and they work great. You can make any size you want, really. He just standardized on those since otherwise guys would start ordering 14.625" barrels if you didn't.

 

Obviously Tromix is the best answer for an SBS. Tony has built thousands of short-barrelled Saiga shotguns.

 

 

Here's a couple of Tony's 10" S-12's.......... The one with the factory foregrip is mine, and it does run great !!!

Still crosses my mind from time to time that I need an 8" gun, though............ Heh, heh, heh..........

 

(Edited to show the stock on mine....)

Edited May 10, 2010 by Jeaux E

[BobAsh 582]

That 10" with the factory handguard and the SPAZ-12 folder is the coolest one around for sure, Joe.

[BobAsh 582]

I think a 10", (or 8-12")folder KISS S-20 would make a hell of a SD/HD cannon. Maybe the best to be had if trustworthy enough. 5 shot in the carry folded position, couple 8's ready to go if something goes real ugly; maybe on some kind of little PDW harness if you were watching a VIPs back in public or running the limo, deploy just like a 74U/Micro Galil/HK-53 type subcarbine or a PDW would be. That's a weapon to restore opinion of the combat shotgun in CQB. Tell me about the SBS 20, interesting to read some specs for little sister. Can never have enough info available.

 

I would've thought there would be special pucks made for these. Also, as far as reliability goes. With a load it takes smooth and spits out the shell, clean gun, etc., do they 'limp wrist'?I saw the video of an AOW pretty much bump firing, but that's not a whole story. Autos(all operation types) have gotten to where you can dump a tube full of dove loads one handed upside down, but with the mechanics and all can a snub nose Saiga? The timing issues from standard brakes, or feeding from a drum? Lot of things going on, in their own time and space, never like precision clockwork...

 

Although Tony has done a handful of 20's, there just isn't much interest in them. It's not any smaller or lighter than the 12, so there's no real advantage IMO unless the recoil is a problem.

 

My SBS runs all the time every time no matter what the feeding device or how you hold it. Brakes and chokes both affect gas; a brake, choke or flashider on the end of the barrel will increase gas and a mid-brake will decrease it.

[joelrod47 373]

That 10" with the factory handguard and the SPAZ-12 folder is the coolest one around for sure, Joe.

 

All kudos to Tony and you for that, Bob !! Tony built it, and you both led me through the initial NFA maze, back when I knew absolutely nothing about it, and what I thought I did know was wrong !!

This gun has more than one special touches on it, thanks to Tony !!!

 

TROMIX IS THE WAY TO GO FOR AN SBS !!!

[03psd 0]

I see lots of 8" and 12" guns but very little in between. Why?

 

Mainly because those are the sizes that Tromix offers and Tony is by far the top maker of SBS Saigas, so most other guys have used the same model.

 

Tony has made a few 10" guns, and they work great. You can make any size you want, really. He just standardized on those since otherwise guys would start ordering 14.625" barrels if you didn't.

 

I have done the trigger conversion to my S12 with Cobra parts. It went very smoothly, however I am not comfortable doing the shortening and gas work. Who do I need to sent this off to have it done right? also it would seem I need tohave my Form 1 approved prior to shipping it off, or certainly receiving it back. Correct??

 

Obviously Tromix is the best answer for an SBS. Tony has built thousands of short-barrelled Saiga shotguns.

 

Form 1 if you are doing the job yourself, Form 4 if you are having it done. Either way you MUST have the paperwork in hand before you can possess a sub-18" gun or you will commit a felony.

 

So on June 1 at 12 noon I send an email and try to get on the list for Tromix (1 of 50 for the month). If I am lucky, I ship off my S12 to OK and my paperwork to BATFE? or does Tromix do it if its a form 4?

[BobAsh 582]

So on June 1 at 12 noon I send an email and try to get on the list for Tromix (1 of 50 for the month). If I am lucky, I ship off my S12 to OK and my paperwork to BATFE? or does Tromix do it if its a form 4?

 

Not exactly...12 midnight is when the list opens; noon may in fact be too late. if you get on the list, Tony will contact you when it's time to send in your gun.

 

Tromix is a Class II SOT, so we can build SBS without taxes. Your "new" SBS will be transferred to you on a Form 4. Tony or Mel will explain the process to you when you get your order in.

Edited May 12, 2010 by BobAsh

[justinmcmillion 77]

I see lots of 8" and 12" guns but very little in between. Why?

I an wanting to go 10" plus a muzzle device. I think the 8" is a bit short and the 12" a bit long.

 

Im with you, the short handguards on the 8" guns look small (Like an f-350 with a ranger front clip) and Im unsure about the long handguards (kinda looks like a kid wearing their dads jacket), but the 12" didnt seem like it would be worth the $200.

 

I ended up registering mine as a 10" and Im super glad I did! It looks very proportional IMO. With a muzzle nut it is similar in size to a krink with the booster installed. The front H&K site is at the front of the handguard which is where it looks best.

 

It looks more like something that could have been manufactured compared to the 8" which looks more like a custom job.

 

Everyone with 8" guns dont leave me hate messages... Id still buy one esp a Tromix all looks aside Im with BobAsh,

 

The shorter the better IMO.

 

If the 6" could be made reliable with all ammo I would have gone that way.

 

These opinions are just my preference based on looks alone

 

The 8" guns will always be the show stoppers

 

I haven't taken any pictures of it yet, but shot some video function testing at the range.

 

http://www.youtube.com/watch?v=fyc4UIabII8

Edited May 15, 2010 by JMac

[BobAsh 582]

Nice job, JMac. I can tell you that the number of (non-pro gunsmith) people that have successfully shortened their own gas system can be counted on one finger.

Also I totally agree on proportion as the major issue. That's why I went with the long Tromix handguard on my 8".





Actually, my preference goes all the way back to one of Tony's earliest guns, when the purpose-made short handguard wasn't available.

It's just a Tapco Galil handguard, and still on of the prettiest guns to my eye.

Edited July 16, 2014 by Juggernaut

[justinmcmillion 77]

Nice job, JMac. I can tell you that the number of (non-pro gunsmith) people that have successfully shortened their own gas system can be counted on one finger.

 

Also I totally agree on proportion as the major issue. That's why I went with the long Tromix handguard on my 8".

 

 

Thanks, I just took a risk and it happened to work out

 

I like how you have a flashlight in yours to fill up the otherwise void in front of the gasblock when using the longer HGs

[BobAsh 582]

 

 

I like how you have a flashlight in yours to fill up the otherwise void in front of the gasblock when using the longer HGs

You can't see it in the other pic, but the green handguard one has an extension welded on to the gas plug. It looked pretty good but I always thought that space would be useful for a light.

Here's a couple of other pics, you can kinda see what I'm talking about.



Edited July 16, 2014 by Juggernaut

[macaholic 5]

Due to all the interest in building your own SBS, I have compiled this thread based on expert testimony. Feel free to add anything that you feel I have missed.

 

How Tromix makes an SBS

I finished up the micro S-12 with the 8" barrel today and took it to the range. The thing ran like a scalded dog with low base target ammo as well as the heavy stuff. The gas system is backed up 4". It cycles perfectly with low base Walmart shells, both Remington and Federal. I also ran some S&B double ought buck through it as well. It runs great.

On NoAim's 12" gun, I moved the entire gas system rearward 2". On the 8" gun, I moved the gas system rearward 4".

There were several guys before me that made S-12's around 12", but all of the examples that I saw, they had left the gas ports in the stock position. I run a single gas port and modify the gas regulator to work like an RPD machine gun. Albeit, the RPD has three gas positions and the S-12 only two. Obviously, the guys got their 12" guns to work, but I have not been able to confirm that they would run on super light 1oz discount ammo. You need a hell of a lot more gas to run those, then the big 3" mags. So, my gut feel is that it will work just fine with high powered shells, but probably will not with the super light stuff, even if a 4th gas port is drilled. The 19" guns have 4 ports anyway. It's the 22" guns that only have 3ea; .113" is about as big as I would want to go before the holes get close to breaking out. 3ea .113 holes will run a 16.5" gun with super light shells.

My personal gun is a 12". I don't care for the blast that comes off those 8" tubes right in front of my face. There is no definitive answer as to how short you can cut the barrel, since the power level of the shell makes such a huge difference as to whether the gun will cycle or not. If you want to shoot bird shot and not have enormous gas ports, the gas block needs to be moved back 2" for a 12" gun and 3.75" for an 8" gun. With that gas port position, you can use the factory .073" size gas port holes. However, if you don't mind running over-size gas port holes and only shoot magnum shells, you can cut the barrel back to 11" and leave your factory gas system as-is.

Yes, the gas system on that gun was moved rearward about 3".That particular gun is a bit of an oddball however. Since then, I have standardized the gas block positions to either 3.75" back on 8"- 10" guns, and 2" back on 11-14" guns.

Move the gas system back 2" for the 12" gun. Then you can run the standard gas port configuration of 4ea .073" gas ports.

Holes are welded up on the 10" and 12" guns. On the 8" guns, the barrel is actually cut off BEHIND the old gas ports.

 

I apreciate all the valuble info on this thread and would like to give many thanks. I am in the beginning process of doing an SBS on my Saiga-12. The Form 1 with paid tax is on the way to the NFA branch of BATFE. I plan to have Tom at Cadiz Gun Works do the job for me and cut the barrel to the factory 16.5' to produce a factory correct Saiga-12 K. He did this gun under warrantee and did such a fine job that the gun runs on 1 oz. low brass Remington with the 19' barrel. The gun was a Vodka special and has three gas ports. I want to use this gun for our monthly subgun matches when we include the shotgun. We only allow the use of low brass bird shot and I would like this gun to continue running the 1 oz. low brass after the barrel is cut to 16.5'. Does two to three inches less barrel make that much difference in back pressure? Any reply would be appreciated.

Edited August 21, 2010 by macaholic