I’m looking to add an MPX to the rotation. There seems to be a few variants Copperhead, Copperhead K, MOX K. I could be wrong. I’m wanting something small, light, that I can add an extended hand guard to and run suppressed. Also would like to be able to add a brace. Any particular variation I should look for or steer clear of? Thanks in advance.

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copperhead is monolithic short rail and no threaded barrel, copperhead K has the same rail but adds a threaded barrel. the MPX K has a replaceable rail and threaded Barrel, I currently have an 8" handguard and can on mine.

Thats the info I was looking for. Thanks

MPX K is 22.5" ~14" overall in length without any brace or stock with a 4.5" barrel with a removable muzzle device (13.5x1 LH) ** measurements from safe

Copperhead K is 22.3" ~13.75" overall in length without any brace or stock with a 4.5" barrel with a removable muzzle device (13.5x1LH) **measurements from safe

Copperhead is 11.8" overall in length without any brace or stock with a 3.5" barrel with a fixed muzzle device

Copperhead K also added three MLOK slots (3,6,9 o'clock) on the monolithic upper for attachments.

One of the other major differences I've noted handling all three of these over time are the rail grooves in the receivers of the Copperheads are smaller than that of the MPX K... If you want to add a collapsing stock and end up going the route of the Copperheads, the SIG collapsing/telescoping stock is not compatible because the bars are too thick to fit into the Copperheads. There once was a specific stock made for the copperheads that is now discontinued and incredibly difficult to find.

There's no way in hell the MPX K is 22.5" in length, with no stock or brace. SIGs posted numbers on their web page will include the brace.

I mistyped. Thanks for the catch.

I edited the post with measurements from what I have in the safe.

Awesome, thanks for the update.

Gotta love how small the MPX series can be.

So I dug a bit further.... I have a Griffin adapter on my MPX which is just about the same size as the factory birdcage (basically within .10")

Length without a stock/brace on the MPX K is nearly 14" on the dot (pictured below)

MPX Copperhead K is ~13.75" factory

Tip of muzzle device to 1913 pic rail on rear of MPX K: