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Hey guys,


Had SIG556 itch for a while, but got cautious after hearing about the issues with early batches (2009-2010?).


SIG556xi got me sold on "Gen2" improvements, mainly: interchangeable caliber barrels (awaiting .300 Blackout kit release) and charging handle (I run mine on the left), longer flat top rail, folding iron sights, ambi mag release and safety.

Frankly, I elected for the "Standard" package, since it had everything I wanted, and I like the feel and look of the polymer handguard (I added Picatinny for USGI Grip Pod).


Gabe Suarez called SIG556 a "Cadillac of AK-s". I see where he's coming from, but wouldn't put it that way.

However, I can also see where Kalashnikov could easily capitalize upon, but instead let SIG cash on the concept.


For starters, "lower-upper" and rigid receiver (with ambi controls on "xi") AR's concept and long sight radius, combined with AK-like gas piston based operation are absolute win-win. Switchable charging handle links the carrier and gas piston: brilliant! 3 position gas port: never got to that point, but "never say never". Nice, rock-solid folder (with AKS-influenced lock, but much smoother fold release button). Added snap-on cheek weld raiser.


Overall, it's a rock solid platform with great ergonomics.



I haven't run it through the vigorous bench testing (not my forte or interest). My SIG groups are tighter than with any of my AKs (5.45 and .223/5.56). 

At just over 450 rounds through, there was only one malfunction, and it's worth elaboration about.

"Tula" casing swelled in and failed to extract after firing, ending up being hard-knocked out with use of the cleaning rod. Happened around 80 rounds count, after moderate rate of semi- fire. Steel casing looked abnormally deformed on one side, starting with neck. Too bad, I didn't take a picture, but few expert loaders pointed out the likely cause (defective casing). Frankly, 1st ever failed Russian ammo...


Last week took it to the local Action Rifle Match, equipped with Aimpoint CompM2. It ran flawlessly and was more accurate than the Operator:)


In two days I'm going back to continue working on my Winchester/NRA Distinguished Expert ("High Power Rifle" category). Posting the picture from the first, opening round: 50 yards "benched" and same while free-standing (no resting against anything or use of sling allowed).


One thing I'm not so happy about is a typical "military-grade" trigger. It's long and heavy, but solid all the way through.

Unlike with AR (and even AK/Saiga) there are only two improvement options are currently available: 

1) Spring kit (lowering the pull from 8+ lbs down to ~4 lbs or slightly lower);

2) Hammer/sear replacement Match-grade kit with crisp and well defined 2nd stage.

Currently, spring loaded "plunger" is set to provide 2nd stage-like feedback to the shooter, and it's adjustable for the pull distance prior to hammer release.


I've got a spring kit, but so far stopped at "plunger" adjustment only and quite like it for the Action Match environments. Might take it further and swap the springs before making the decision on upgrading the hammer and sear.


I replaced factory three-prong flash hider (more effective than the standard "bird cage") with Manticore comp, but despite its claims I noticed the "fireballs", even though swap resulted in much improved muzzle control and .22lr-like recoil.

I might try it with my ever-trusting Miculek comp next.


Overall, I'm a "happy camper", placing this boomstick into my definite "go to" rifle category.


Happy Shooting!






Edited by Sgt. Raven
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Very nice going that route as well. See flash hider and a comp. Much difference.?


SIG's OEM flash hider is excellent for what it's designed for: flash suppression. Recoil is manageable and the muzzle jump is nothing unusual and somewhat compatible to AR with the "bird cage" on 16" barrel.


Comp brought the sweet memories of last Independence Day: fireballs and (un)holy "boom".

So far I only shot .223, but bringing the 5.56NATO (XM193) along to compare both tomorrow.

When compared to the flash hider, this comp wipes out the recoil to .22lr level. 

Muzzle is tamed and stays put and right on target. I only used this comp for the Action Rifle match; therefore, no "static work", while monitoring via red dot. Will check tomorrow.

And it's loud. Not as M82 Barrett though smile.png

It doesn't have the dynamic pressure of side-ported comps, but blows the "boom" in ~270 degrees "aura" (since two bottom sections are solid).

My neighbors at the range will hate me. Oh well...



Happy Shooting!


P.S. I also replaced SIG's pistol grip with Hogue overmold (fingerless; not pictured yet). I like it better, plus easier to reach and work the safety.

Edited by Sgt. Raven
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I have had case out of spec issues with Tulammo in the past. My experience was that the length of the neck can vary between different cases. My guess is that this can potentially change the final clearance of the bullet to the leade when chambered, potentially increasing/decreasing chamber pressure. An OOS case neck can appear to be undercharged, and fail to cycle the action, or the case may expand too much due to overpressure and fail to extract.


Depending on what factory it comes out of, Russian steel .223 QC does not appear to be as high as with steel 7.62x39. Tula/Ulyanovsk have been the worst for .223. I have had the best overall experience with Barnaul ammo, so I try to find Barnaul manufactured .223 if I'm going to shoot steel case ammo. Most WPA .223 is coming out of Barnaul these days.


Beware.. The increased barrel wear due to the copper-cladded Russian .223 is a very real thing. The jacket is a very mild steel with a thin copper wash, and is not as gentle on the bore as a true copper-jacketed bullet will be.

Edited by mancat
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Great info, Mancat (as always).

Didn't know about such variations. Good point on "copper wash".


Frankly, I stopped buying russki ammo, but mostly for political reasons. Plus it's dirty as Satan Mom's arse.

Kept wasting what I still have, but started trading it 2 for 1 for quality ammo.

And speaking of: with quality ammo prices plummeted after late market saturation, I'd much rather pay few pennies more for US-made ammo (but not snubbing the free-world brands as well). And with some crazy deals over the internet and local "-mart", the good ol' "Starred and Striped" is getting easier on wallet, and so on the barrel, plus supporting American jobs in the industry, which is PITA for current commies in charge.

Edited by Sgt. Raven
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With Primary Arms' 1-6x red dot, Hogue fingerless overmold PG and Manticore Arms' NightBrake comp.

PA's cantilever had to be flipped backwards to get the mounting knobs out of the way of the left-side charging handle.


As-equipped for Winchester-NRA Distinguished Expert qualification course (tonight!). 



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WIN-NRA qual course is going slow, but steady. So far only two "DE" levels (over 170 pts) complete out of 10 (50 yrds free standing is tough, but getting better).

See last lucky run pictured.Elbow rest on sitting: no bench rest allowed.


Comp must go: too much flash. Going back to the good ol' trusted Miculek.

Any takers on the Manticore Arms NightBrake? Used twice; ~ 120 rounds through. Still a very good comp, just not to my liking...




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  • 1 month later...
  • 3 months later...
Please tell me again how crappy SIG556 factory trigger is... 


And yeah, I know, it's not Geissele or Timney smile.png


Edited by Sgt. Raven
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CONGRATULATIONS regarding your shooting success with the SIG 556xi.


In the event you are not aware, there are a few 'other' aftermarket products available for your rifle:


Sear & Trigger:  http://shop.shootingsight.com/SIG-556-556XI-551-A1-556R-Sear-Hammer-SIG-556-551-A1-Sear-Hammer.htm


Krebs extended safety lever:  http://www.krebscustom.com/products/31/Krebs-Custom-Extended-Safety-for-Sig-550-556-Series


SIG 556xi charging handle by TROMIX:  http://www.tromix.com/sigsauer-parts.htm

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CONGRATULATIONS regarding your shooting success with the SIG 556xi.


In the event you are not aware, there are a few 'other' aftermarket products available for your rifle:



Thank you!

One more thing to add is a German made spring kit (by "scorotech"), compatible with existing (factory) and so the Al's set.

I wish there was something designed as AR's drop-in kit.

Opportunities are there, now what we need is a market-driven demand.

Happy Shooting!

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