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SIG 556 Classic, by Pat Cascio

Anyone who knows even a little bit about real battle rifles, knows that the Swiss military has issued the SIG Sauer STGW90 for years, and that it is still being used. The original STGW90 was the envy of gun owners – who, of course, couldn’t own them. First of all, they couldn’t be imported into the USA. Secondly, they were select-fire – a big “no-no” in our once free country. The Swiss also developed a semi-auto only version, known as the PE 90 or SIG 550/551. Still, American gun owners lusted for one of these rifles. Only a few hundred SIG 550 and 551 rifles were imported before an import ban. SIG Sauer finally came out with a semi-auto version in the USA, and called it the SIG 556. This was available in several different versions.

I elected to get the Classic version of the SIG 556, after checking out one at my local gun shop. I was quite impressed with it, compared to all the variations of AR-15s on the market.

Of course, make no mistake, SIG Sauer [1]firearms are not cheap, by any stretch of the imagination. Prices have come down some, since many are now made in the USA, instead of Germany, but they are still spendy! As I recall, the SIG 556 Classic model was retailing for around $1,800, and that was a big chunk of change, no matter how you look at it. I ordered a sample from SIG, for an article several years ago, and in short order, my sample arrived. It was more than I expected it to be!

But there are usually problems in many new guns. In this case, there was unusual wear on the bolt carrier. It wasn’t anything to really be concerned with – it was self-limiting after a short time. One really nice thing was that the 556 was redesigned to take AR-15 magazines, instead of the nearly impossible to find, SIG 550/551 magazines. So good on SIG for being smart enough to do this for American shooters.SIG 556 RifleLet’s take a look at the specs on the 556: First of all, as already mentioned, it is a modified version of the Swiss  550/551 – one of the great battle rifles of our time. And, it is chambered in 5.56mm – and the gun will also fire .223 Remington ammo. It operates using a gas piston, not a direct impingement gas system. This gas piston is more reliable in my humble opinion, and it doesn’t allow the gun to get nearly as filthy as an AR does. The gas piston is also adjustable, if need be, for a dirty rifle, or poor ammo. The 16-inch barrel is hammer forged, so it will last a long, long time, before having to be replaced – if ever! There is no separate charging handle, like you’d find on an AR-15. Instead, it has a charging handle on the right side of the gun – attached to the bolt, and it is quick to chamber a round. Another advantage is,that the 556 is easy to field-strip for cleaning or minor repairs.

The barrel has a flash suppressor that works quite well. On the opposite end, we have a telescoping stock, that also folds to the side. That is super kool, if you ask me. SIG made several changes to the stock, and on the model I’m reviewing today, it is a slightly different stock than the one that came on the first 556 samples. My sample has storage compartments for batteries for optics. We have a short Picatinny rail on the top and bottom of the polymer fore end.

Marginal Sights

There are also factory folding sights – front and rear, but in my opinion they both are really lacking. On my sample that I’m reviewing here, the fold down (flat) rear sight was missing – but it was a garbage design to start with. The front sight also folds down, but it is only adjustable for windage, not elevation – and that is poorly-designed, too. SIG says this 556 weighs in at 8.2 pounds – and the weight is forward. So the gun doesn’t balance as nicely as an AR does.

My original 556 that I purchased is long-gone. I did purchase my sample that SIG sent me, but they don’t really offer gun writers that great of a price on gun samples if we wanted to purchase them. Long story short…and I could be off on my numbers a bit, but I seem to recall paying around $1,200 for my sample. However, several months later, SIG dropped the price on the 556 – and you could find them all over the ‘net for $999. So I politely asked SIG if they would refund some of the money I paid for my sample. That wasn’t gonna happen. So, I ended up later selling my sample for what I had paid for it.

Not too long ago, my local gun shop got a SIG 556 Classic in a trade, and whoever owned it, had the rifle professionally painted in various camouflage colors. It was nicely done. And, the price – well, it was well below what I thought it should sell for. So in short order, a deal was struck and it was mine. However, I really forgot how poorly balanced the SIG 556 was – but I could overcome this…or so I thought.

SIG 556 RifleMake no mistake, SIG Sauer, produces firearms that give outstanding accuracy, and they are made to last a lifetime. They are “that” good when it comes to quality. With no rear sight on this 556 used sample, I put on an AR 15 fold-down adjustable backup rear sight. However, it was height mismatched, causing the gun to hit about 8-inches high at 50-yards – not good! I couldn’t find an original fold down (flat) factory rear sight, so I installed a SIG Romeo 5 red dot sight [2] on the upper receiver, and I quickly had it zeroed. BTW, these sights from SIG are a bargain, compared to many other red dot sights on the market.

Barrel Specs

The 556 comes with a 1:7-inch barrel twist, so it can shoot the heaviest 5.56mm and .223 Rem bullets that you care to put through it. From Black Hills Ammunition [3] I had the following .223 Rem ammo on-hand. 50-gr Hornady V-MAX, 55 gr FMJ – both brand-new and factory seconds, and once again, factory seconds are still brand-new ammo, but just have some cosmetic blemishes, I had 55-gr Soft Point, 55-gr Barnes TSX, 60-gr Soft Point, 60-gr Hornady V-Max and 68-gr Heavy Match Hollow Point – so a good mix of ammo to run through this SIG 556.

SIG 556 RifleIn all my shooting, and I had several volunteer helpers, we fired 500 rounds through the SIG 556 in a couple of hours. One shooter, who is short, had a tough time holding and steadying the 556 – he is really short! But he did a fair amount of shooting. We did accuracy testing at 50 yards, because we didn’t want to walk out to 100-yards to keep changing targets. We used a big boulder, with a padded rifle rest on it for accuracy testing. By teh way, I only publish my own results when it comes to accuracy, so if there is a problem, I take the heat. We also killed a lot of rocks and fallen trees in our shooting. Lots of fun just shooting targets of opportunity like that, and of course unleashing 30-round magazines as fast as we could pull the trigger is always a good test on how a gun will function when it gets good and hot. There were no problems with the SIG 556. There was not one failure to feed, or eject – it just perked along without fail.


Best accuracy was the Black Hills 55-grain Soft Point. I had been hoping it would be their 60-gr Soft Point, as hat has always been a great accurate round for me in ARs. At 50-yards, using the SIG Romeo 5 [2]red dot sight, I had groups really close to half an inch most of the time – some were bigger, some a tad smaller  and the bigger groups – that would be my fault. The largest group was an inch with the 50-gr Hornady V-MAX and it was slightly over an inch – which means two inches at 100-yards – which is still good accuracy for a battle rifle.

My volunteer shooters really liked the 556, even our shorter shooter. But everyone complained that the gun felt heavy, and especially front end heavy. I had to agree! I had forgotten about this from my original 556 that I purchased direct from SIG. In the end, after owning this 556 for several months, I decided to trade it off for something else that caught my fancy. However, one again, I kind of regret not keeping it – it is still a great gun.

I checked around the ‘net and found brand-new SIG 556 samples for $1,300 and used ones for $850 and up. I won’t reveal how little I paid for my used SIG 556 – but it was a bargain.

If you want something a little different than an AR or an AK, then check out a SIG 556 if you can find one. SIG Sauer has long discontinued this model. I believe that they scared a lot of people away with their original price tag. That is too bad, since it is a great gun.

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#1 Comment By ww On September 9, 2019 @ 12:40 pm

My Springfield Armory socom is heavier, I love my sig 556 swat it has metal forearm with rails.
I will never sell it, it’s easier to clean than a AK!
And very accurate. Every one wants to shoot it when I take her out.

#2 Comment By LivingOnTheFault On September 9, 2019 @ 3:24 pm

I put Arms (Rear), and Samson folder on mine. Placed 3.5 x 10 x 44 Zeiss Conquest on it. I would like to purchase a spare part kits from it. May possibly change out the rear sight for Sig diopter sight, and I like the looks of the folder better than the M4 Style stock. Their Sig 522 looks to be a good training weapon as well. Recoil is different than AR15 (M4) style rifle, and more pleasant to shoot.

#3 Comment By Sigproshooter On September 9, 2019 @ 11:10 pm

Stone dead reliable. If this weapon is too heavy to employ properly, you’re entirely too soft now for the things to come. Change that now. Life will be harder than most conceive. I shake my head when people complain about the weight of a carbine caliber weapon. These are the good old days. Use them.

#4 Comment By Live free or die ian On September 9, 2019 @ 11:16 pm

I have put a sig romeo 5 on every ar style long gun I own. It is fantastic.

#5 Comment By Bwhntr64 On September 10, 2019 @ 1:58 am

So let me see: it is a great gun, but you got rid of it. Front end heavy which must have really bothered you. So in reality it was not so great after all, from your perspective at least. Sort of an odd review. I own a very nice SIG 220 Elite in 10mm, and this is a very nicely done pistol. I agree SIG quality is top notch. But this review does not encourage me to buy this particular weapon.

#6 Comment By PCBRIG On September 10, 2019 @ 2:44 am

Sounds like a competent rifle, which isn’t surprising coming from Sig (I’m a “Sig guy” myself; really love their pistols). However, the author doesn’t acknowledge there are many great piston ARs out there (in various calibers, to include 5.56, of course). I carried M4s in combat in both Iraq and Afghanistan and they never let me down, but I hated the direct impingement feature (unbelievable fouling, heat, etc.). I never would have bought an AR for myself had there not been excellent piston alternatives out there. My POF and Ruger ARs are superb. As for optics, it’s a free country I realize, but it’s a shame Sig sources their optics in China. I’ll scrimp for the real thing (Aimpoint, EoTech, Trijicon) and be certain to have the performance, quality, and durability that comes with each and take a lot of satisfaction knowing I’m supporting American workers and American manufacturing. China is our enemy across the board; why buy their cr*p?

#7 Comment By Ralph On December 30, 2019 @ 5:56 pm

I just acquired a SIG 556 Pistol. I’ll be adding a folding stock adapter and a SBA4 pistol brace. I’ve already installed an EoTech 512. This will be an outstanding GHB/Home defense weapon.