sig sauer mpx

Sig Sauer MPX Firearms

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SIG MPX Firearms

The SIG MPX is SIG’s 9mm piston firearm. The MPX runs a short-stroke piston and AR-style controls on 9mm, with magazines that are SIG’s own MPX pattern. It does not take Glock, P320, or AR-15 magazines. The top rail is optic-ready. A factory optic is not installed. Pistols ship with SIG’s folding PCB. The SBR uses a stock and needs NFA paperwork.

Copperhead is the shortest pistol, with a 20-round magazine and SIG’s folding PCB. The MPX K is a 4.5 in. threaded barrel with a Timney trigger and a 35-round magazine. The PCC is a 16 in. carbine with a folding telescoping stock. The Off-Duty K is only for eligible buyers. The SBR is the 4.5 in. gun with a folding stock, so it needs NFA paperwork.

How to choose

Copperhead and the MPX K ship with SIG’s folding PCB and go to a regular FFL. The PCC is a 16 in. rifle. The SBR is the short barrel with a stock. None of them take Glock, P320, or AR-15 magazines. A factory optic is not installed. See also SIG Sauer pistols and SIG Sauer rifles.

Frequently Asked Questions

What is a SIG MPX?

The MPX is SIG’s 9mm short-stroke piston firearm with AR-style ambidextrous controls and proprietary MPX magazines. It is not an MCX and not a blowback 9mm carbine.

What is the difference between MPX K and Copperhead?

Copperhead is the 3.5 in. coyote pistol with a 20-round magazine and a built-in muzzle brake. The MPX K is the 4.5 in. black pistol with a Timney trigger and a 35-round magazine. Both ship with SIG’s folding PCB.

Is the MPX a pistol or a rifle?

Copperhead and the MPX K are pistols. The 16 in. PCC is a carbine. The 4.5 in. model with a folding stock is an NFA short-barreled rifle.

What magazines does the MPX use?

SIG MPX magazines only. They are not Glock, P320, or AR-15 magazines. Copperhead ships with a 20-round magazine. The K, PCC, and SBR in this group ship with a 35-round magazine.

Does the MPX SBR need NFA paperwork?

Yes. The 4.5 in. MPX K SBR is an NFA short-barreled rifle. It ships to a Class III / SOT dealer and needs the proper transfer and approval before you take possession.

Do I need an FFL to buy an MPX?

Yes. Pistols and rifles ship to a licensed FFL. The SBR also needs the NFA transfer. The Off-Duty MPX K is limited to eligible buyers.