The SIG P226 is chambered for 9x19 mm parabellum, 40 S&W and .357 SIG. The P226 itself has many other varients the P228 (m11) and P229 are both compact versions of the staggered-column P226.
The P226 and its variants are in service of many law enforcing agencies through out the world.
The P226 was designed to replace Colt 1911 (M1911A1) as the primary side arm for US armed forces. The XM9 service pistol trails that were held by US Army in 1984 to find the replacement for Colt 1911. Only the Beretta 92F and SIG P226 satisfactorily completed the trails.
But the M9 contract was awarded to Beretta 92F Due to its lower total package price. The P226 costs less per pistol then Beretta 92F but SIG's total price package with magazines and spare parts was higher then Beretta's.
How ever the Navy Seals chose to adopt P226 later.
The P226 operates on a locked breach short-recoil mechanism.
When the bullet is fired its cartridge pushes against the breach, this forces the slide and barrel to move backwards which are locked together, after the backwards motion of few millimeters the barrel is cammed down and slide is released, and at this point the bullet leaves the muzzle and the gas pressure levels drop to safe levels, by then slide gains enough momentum allowing it to move backwards freely on rails. The slide then completes the ejection of used cartridge and feeding of the new one.
Instead of lugs and recess in barrel used by many other short-recoil operating pistols the P226 uses an enlarged breach section which locks in ejection port.
The Variants of P226:
P226R (railed):
Its the same as normal P226 except it has a rail built in front of the trigger guard, it is how ever slightly different form the standard rails used for accessories, but since most of the accessories fit in it, It has now become a standard P226.
P226 Tactical:
Its a P226R with an extended 127 mm barrel with external threads to accept suppressor.
P226 Navy:
The P226-9-NAVY is a version produced for Navy seals, with the same specification including phosphate corrosion resistant finishing on internal parts, contrast sights and stainless steel slide engraved with an anchor that shows its a Navy seal weapon.
P226 Mk25:
Mechanically and functionally its same as P226 Navy, it was advertised by SIG as an identical weapon as one carried by navy seals to allow their sail in public.
In other words its same gun with a different name, the only thing that actually makes it different is the anchor on the slide.
P226 SCT:
P226 SCT (Super capacity tactical) is an all black, Nitron finished gun, with a SIGLITE rear night sight and Tritium fibre optic front sight. And comes with a 20 round magazine of 9mm parabellum, and 15 round magazines for .40 S&W.
Its as if it was made to hunt in the Dark.
P226 Equinox:
Its a two toned gun chambered for .40 S&W, it has SIGLITE rear night sight, Tritium fibre optic front sight, accessory rails and grey wooden grips.
P226 ST (stainless):
Its a complete stainless steel version of P226. which was produced in very limited numbers. Its claimed to have reduced recoil since its frame was built by stainless steel instead of aluminium which increases its weight and weight reduces the recoil felt, this lets the gun return to target very faster compared to al versions of P226. This feature made it a very practical choice among the competitive shooters.
Its not currently manufactured any more.
P226R HSP (homeland security pistol):
Its the same pistol as were given to the department of home land security. It only has a limited production of 1000 guns. It comes with an american flag engraved on the gun.
The HSP also features a new DAK trigger, stainless steel slide, with SIGLITE night sights with light weight alloy frame with rail.
P226 X-Five:
Its comes with 127mm barrel and slide, beaver-tail grip and adjustable sights. It is designed only for competitive shooting. It is custom hand fitted in Germany which results in increased accuracy.
P226 X-Six:
It is a precession pistol designed for competitive shooting, it has extended slide to accommodate with its 152 mm barrel.
It also has grip groves engraved in front of the gun and low profile adjustable sights and light weight magazines extension.
P226 Elite:
The P226 Elite adds an extended beaver tail, custom wood grips, adjustable night sights and short reset trigger. The engineers designed it to have only 60% of trigger reset, this helps in rapid firing. The P226 is available in 9mm parabellum, .40 S&W and .357 SIG.
P226 Combat:
The P226 Combat and P226 Combat threaded are both available in single action/double action triggers. It comes with night sights, nitron finished barrel and slide. Desert tan polymer grip and military standard picatinny rails as well as phosphate coated internals. They also have 15 mm extended barrels with external threads to accept sound suppressor.
P228 (m11):
The compact version of P226, the P228 is in use with many law enforcing agencies around the world and also US military designated as M11. It has shorter slide compared to P226 and is only available in 9mm parabellum.
The M11 will be replaced for air force by the modular hand gun program.
P229:
Its a compact version of P226 used for conciled carry purposes, it comes with a DA/SA trigger but it is also available in DAK version.
All of the versions of P226 are also available for P229. The P229 differs form its cousin P226 in various ways. and is available in all 9mm parabellum, .40 S&W and .357 SIG. and it can be converted between bullet types by a simple barrel conversion.