Sig MCX questions

I am really interested in getting a Sig MCX. My end plan is to have a internally suppressed 16" overall length barrel or ~11" barrel with permanently attached suppressor. I have thought about just trying to get an 11.5", but as a civilian it appears that I can only get it with the arm brace, and moving the "pistol" to a SBR, or regular rifle with permanently attached barrel is a potential grey area that I do not want to F with.

Next question is the gas system adjustable where the 16" barrel could be cut, suppressor installed and welded, then retune for suppressor. ? From what I had sound the 11.5" with the Sig suppressor is supposed to be GTG with no problems. Almost seems like getting the MCX 11.5" pistol, make it SBR, get the aluminum framed skeleton butt stock, and suppressor would be the most legal and simple way to go. With the SBR I am venturing into something I have not had before.

Thanks !


Gunny Sergeant
If your end game is an SBR, get the pistol and do the paperwork. Even though I'm selling one of my 16" 5.56's, that's the best option. I really don't know the answer on the 16" being cut, although you could always sell the 16" and get a 11.5 barrel. I have the .300 pistol, and it's one of the favorites, fun to shoot. They are nice guns, according to SIG, it will be supported even tough the Virtus is the latest model. To my understanding the bolt carriage upgrade has the newest version (as in the Virtus) bolt and will work if you decide to get a barrel upgrade, which is a moot point because the barrel upgrades will come with a bolt.
Thanks Mark! So the upgraded bolt is the same as the Vitrus bolt? Looks like you can buy barrels for $600. But if I bought yours I have the stock I want and the hand guard. I'm still hoping to pick to
yours up. Do you know if the gas block on those is adjustable?


Gunny Sergeant
All of the MCX and new Virtus have the two position blocks. The intent is suppressed and unsuppressed. The Sig manual specifies where it should be depending on what you are doing. They are not adjustable as in the FAL style or an AR with an SLR block as one example with multiple positions. Yes on the bolt. Hope that helps. Yeah the bolt lugs have a radius on them to do all the things a bolt does during the cycle of operation more efficiently and with longer service life.
Get one of the short barrel 5.56 or 300 BO pistols and a stamp so you can add a stock OR
get one of the rifles and a stamp so you can do a short barrel conversion.
Same end result. The barrels are super easy to swap and each comes with an integrated gas block and piston.
Swap calibers, barrel lengths, handguards and braces/stocks as easy as changing your underwear -- and a lot more fun. Two bolts for the barrel change and one bolt for a stock/brace swap. You can change hand guards to get different lengths or even a fat one to fit your suppressor into.

For the pistol, I like the Shockwave brace as a substitute for the SIG brace as it is much lighter and folds nicer. With the stamp you get a few more REAL stock options.
It's a great system, but a lot more expensive than even a "good" AR. If you have the quid, it's well worth it.

Get a F.A.T. torque wrench if you are going to do barrel swaps.
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Thanks David! The no buffer tube and folder is the big bonus for me. I'm going to buy the rifle, with 16" barrel for now. Then I can shorten and suppress later.
Better look at their new version -- Virtuis or something like that, before you decide. I'm happy with the present version as mine runs fine and the new one has a heavier barrel and other mods. Their is a discussion or two on SIG Talk.