Tag Archives: AR 556

The SIG P556 Pistol, settling the 9 over 40 argument once and for all

How many times have you personally weighed in on the subject of what is better in a handgun, more powerful, etc., the 9mm, .40S&W, or .45ACP? Well SIG would have to weigh in on that with their P556 and bring something very different to the table with one of the coolest pistols on the planet.

(Yes, its a pistol. We promise)

(Yes, its a pistol. We promise)

What is it?

Based on the company’s proven SG 550 series rifles, the P556 is a 5.56mm NATO caliber pistol (yes, pistol) that is totally ATF compliant. Since it does not have a traditional stock that is pressed to the shoulder, the ATF’s rules on short barreled rifles (SBRs) do not apply so there is no minimum length required by law for the gun or barrel. This means it can be as short as the specs allow which is about 27-inches and change with the option of adding a stabilizing forearm brace.


Since it comes from the SG550 lineage, let’s talk about what that means. Remember the SIG 550 series is a hybrid between the AR15 and AK47 design. Although very AR-like in form (and take down), its internals are quite different. Instead of direct gas impingement, the series uses a long stroke piston-operated rotating bolt locking mechanism very similar to that of the AK. This, in an abbreviated version, is the P556.

Compact and handy, this pistol will accept all standard AR style mags

Compact and handy, this pistol will accept all standard AR style mags

The gun is top notch in its construction and has more features per square inch than any two more common guns of the same size combined. The pistol’s receiver is made of high strength steel with SIGs well known black Nitron finish. Its trigger housing is machined from an aircraft grade aluminum alloy forging. A 10-inch button barrel with 1:7 twist is just long enough to stabilize 5.56mm rounds, although be prepared for a significant muzzle blast.

The 18-inch sight radius, while much longer than what you would find on a pistol (a Colt 1911 has an 8-inch radius for instance), is still much shorter than on a carbine. A two-stage trigger and ambi safety make for good surface controls while the magazine well will accept any standard AR/M16 style mag. The flash hider unscrews and has a .5 x 28 TPI thread pattern under it which will allow you to swap out other muzzle accessories (flaming pig anyone?) while a MilSTD1913 top rail gives a good optics platform.

The rear endcap unscrews to expose threads for any AR-style buffer tube 1.0" - 1.2" in diameter (All NFA rules apply!)

The rear endcap unscrews to expose threads for any AR-style buffer tube 1.0″ – 1.2″ in diameter (All NFA rules apply!)

The P556 makes a great platform to buy and later turn into an NFA registered SBR. Once you get your stamp (which currently is taking up to a year) all you have to do is just unscrew the back cap on the receiver and add any M4 style buffer tube/stock combo as it’s already threaded for one. While it may be tempting to go ahead and do it without a stamp, watch out as this can get you some non-negotiable federal time.

SIG makes two versions of the P556, the Classic and the SWAT. The primary difference between these are noted in the specs below


The SWAT P556

The SWAT P556


The Classic P556 with its Swiss style handguard

The Classic P556 with its Swiss style handguard


  • Barrel Type: Button Rifled Barrel
  • Flash Suppressor: A2 Type
  • Forearm:  Polymer Swiss Style Handguard (Classic) Aircraft Alum Quad Rail (SWAT)
  • Weight w/out Mag: 6.8 lbs. (Classic) 7.2 lbs. (SWAT)
  • Operating System: Full Length Gas Piston, Rotating Bolt
  • Overall Length: 28.25 in (Classic) 27.25 (SWAT)
  • Barrel Length: 10.0 in
  • Rifling: 1 in 7″
  • Sight Radius: 18.1″
  • Mag Capacity: 10 Rounds standard, but accepts all NATO STANAG mags and drums.
  • Features: SB15 Stabilizing Brace, SIG branded Mini Red Dot Sight
  • MSRP: $1,340.00 (Classic) $1,471.00 (SWAT). Street price about 20% less.
  • CA/MA Compliant: Yeah right

Pros and cons

Well this thing is cool first of all. I mean it’s all but an SBR minus the full sized stock and tax stamp headaches. It tucks away in a center console or under a seat in a car or truck, cuddy cabin of a boat, or in that space between the nightstand and the bedside very nicely. Put a 60-round Surefire coffin mag in it and you are just good to go for any home defense scenario you can think of from a wayward burglar who didn’t realize someone was home to a full out Red Dawn style invasion or zombie apocalypse. Plus it’s darn fun at the range and always a crowd pleaser.

They are a quantum leap from the Draco and MVP style AK pistols while being able to fire standard 5.56mm ammo and take STANAG mags.

On the downside, it’s heavy for a pistol and too big (unless you are a fan of parkas and CQB slings) to carry concealed. When shooting at night you are blinded by the fireball spitter that is the gun’s 10-inch barrel. Further, it’s too small and inaccurate, due to not having a stock, for serious work as a rifle. So it’s one of those neither nor type of things. Plus the cheapest you can touch one is about $1100 if you shop around– which is the same cost as an entry level AR and a decent CCW pistol combined.

Still, you know you kinda want one.