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Sig built this folding knuckle to solve a common headache: how to run the brace or stock you actually want on an MPX or MCX and still get it folded down for storage or a smaller case. It clamps onto the vertical 1913 Picatinny section at the rear of your receiver, then accepts a standard mil-spec buffer tube so you can thread on the brace of your choice. The whole thing is machined from steel with a matte black finish, so there's no flex or plastic to worry about once it's locked in.
The appeal here is versatility without the fuss. Instead of being stuck with the stock or brace that came on your gun, you can swap in whatever mil-spec buffer tube setup you prefer and pick your side for folding. Owners consistently mention how solid the lockup feels, opening and closing with a positive detent that stays put rather than flopping around. To fold, you grab the buffer tube, apply a little pressure to the knuckle, and it swings over clean. Pop it back and it cams into the open position with a firm click.
Installation is refreshingly simple. The adapter slides onto the rear Picatinny rail and locks down, and the buffer tube threads in and gets held by a set screw, which skips the frustration some folks have with fighting a castle nut in this application. A hex wrench and a few minutes is all most people need. It's a favorite for turning an MPX or MCX into a more compact, packable build, and thanks to the universal 1913 interface, plenty of owners have run it on other railed platforms like PC Chargers and various pistol builds with good results.
Since this is a genuine Sig part, fit and finish match the rest of your gun, and the steel construction means it holds up to hard use without complaint.
It mounts to the vertical 1913 Picatinny rail on the rear of your Sig MPX or MCX receiver. The adapter slides on and locks down securely. From there you thread in a standard buffer tube to run your chosen brace or stock.
No. The buffer tube threads directly into the adapter and is held in place by a set screw, so you skip the hassle of wrestling a castle nut. You'll just need a hex wrench to snug down the set screw during install.
Yes. Because it uses a standard mil-spec buffer tube, you can run most AR-style braces and stocks that thread onto a mil-spec tube. Owners have paired it with a wide range of buffer tube braces and fixed stocks with good results.
It locks up tight in both the open and folded positions with a firm, positive detent. To fold, you grab the buffer tube and apply light pressure to the knuckle and it swings right over. Opening it cams back into place with a solid click, and there's no wobble once it's set.
| UPC | 798681551163 |
|---|---|
| Manufacturer | |
| Manufacturer Part Number | ADAPTERXFOLD |
| Color | Black |
| Length | 2 |
| Model | |
| Package Height | 2.6 |
| Package Width | 3.9 |
| Product Type | Accessory-Stocks |
| Shipping Weight | 0.395 |
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