SIG Arms ACP Kit to turn any Railed Pistol into a Carbine

By Shooter, Jan 30, 2012 | |
  1. Shooter
    Introduced this month at the SHOT Show industry event, SIG ARMS/SIG Sauer of Exeter New Hampshire has debuted their revolutionary new Adaptive Carbine Platform or ACP. Now pistol-to-carbine conversion kits are not new on the market. Companies like Hera Arms, Stellar Rigs and Mech Tech have sold carbine conversion units for years that take popular handgun platforms such as the 1911 and Glock 17 and create a more stable PDW type of weapon. Most of these designs however take a basic pistol and change the slide, barrel, magazines and many other features to create a Franken-gun weapon that is neither rifle nor pistol, but all PDW.

    For those head scratchers out there, the Personal Defense Weapon (or PDW) concept was the 1980s era school of thought that soldiers on the battlefield not directly in combat needed an effective weapon larger than a pistol and smaller than a rifle for....wait for it: Personal Defense. From this concept came the shorty H&K MP5K series, FN's 5.7mm P90, the micro Uzi and the Steyr TMP among others. A PDW was that 'in between' sort of missing link in firearms development.

    Where SIG's new ACP platform changes things is that it does not replace the barrel or slide of the pistol in question and is not strictly limited to a single family of pistols. The clever design takes virtually any modern handgun with a under barrel accessory rail built into the frame and converts it by adding the ultimate series of accessories- the ACP itself.
    - SIGs new ACP PDW platform, taking a standard railed pistol and enveloping it inside an adapter that gives more positive control and options for accessories. (photo by SIG Arms)

    Without modifications simply take your handgun and insert it into the ACP with the adapter clamp that you fit to the rail, lock it in and you are good to go. On SIG's instructional video, which very slowly walks you through the installation, it takes about 1-minute. Black anodized aircraft aluminum construction keeps the weapon's overall weight low.

    The main advantage that the SIG ACP seems to bring to the ballgame is rails, rails and more rails. There is a full-length accessory M1913 rail running almost 8-inches down the 12 o'clock position along the center top of the platform. Smaller M1913 rails run along the three, six, and 9 o'clock positions giving you options to mount anything you want on the little beast. With the Broomstick style forward mount, magnification optics, flashlights, lasers, reflexive sights or just about anything else you want to run you can trick out your handgun fast.

    You still have access to all of the original controls of the firearm on the firearm itself including safety-decock, magazine release, and slide release. The only interface between the ACP and the handgun inside is the charging handles, located on both the left and right, which chamber the pistol slide inside the platform when cranked back. When not in use, the charging handle can be folded forward, flush with the ACP.


    The SIG ACP charging handle in action. (photo by SIG Arms)
    The ACP is set to come out currently in three models:​


    - The basic model that includes the ACP itself and the rear sling point. It allows for fast, easy conversion and works with most railed pistols. Demonstrated pistols included all SIG P-series pistols (with rails), the full sized Smith and Wesson M&P, the full-size Glock 19/21/22 etc., and M1911s with rails such as the Springfield Operator series. Although the system is modular and is billed as being usable with most railed pistols, each weapon system needs to have its own adapter block to be installed. Suggested retail is $369, which means that you may be able to get into this basic model for as low as $275 when they become available if you shop around. Overall, not too bad for the functionality and less for what you could by most reliable PDWs themselves for. If you own several railed pistols the nice thing about it is you could acquire one ACP and swap it between your Glock, Sig, Smith etc.
    ACP-Enhanced - The Enhanced version includes the new SIG SAUER MIL-GRADE Mini Red Dot Sight, a quick detachable sling swivel, and a Single Point Bungee Sling. This version is MSRP for $499.​


    ACP-LE -
    This National Firearms Act-regulated military/law enforcement only model features the really neat top- folding shoulder stock. It is this stock that makes the platform a NFA Class III item and any civilian purchasers have to follow all the same requirements for registering a short-barreled rifle or SBR with the BATFE. No pricing available for this version. Odds are if you have to ask...

    For more on SIG SAUER, please visit

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