(Rob Curtis / Staff)
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TAMPA — Sig Sauer quietly showed their new PDW, a short stroke push rod, multi-caliber, integrally suppressed carbine that has yet to be named. MCX would be a likely choice for the carbine's name based on Sig's current naming convention.
The compact carbine is multi-caliber capable with the bolt and barrel change happening at the end-user level. The end-user can switch between 5.56 NATO, 7.62x39mm and 300 AAC.
The design uses Sig's short-stroke pushrod operating system. It still has a Stoner-style rotating bolt but features a gas tappet that regulates the gun's operation. In fact, the upper is fully compatible with an any AR lower.
Though Sig employees were careful not to reveal the inner working of the design, it seems obvious that the system also replaces the AR's lower receiver-based buffer system with a more compact arrangement that resides completely in the upper receiver. This allows for the use of a completely collapsable or folding buttstock.
One of the challenges overcome by Sig is the ability for the, essentially, bufferless operating system to run suppressed or unsuppressed. Sound suppressors increase gas pressure in the operating system and speed up the guns operation. Removing the buffer system reduces the operating system's ability to compensate for the swing in gas pressure. A compact system would easily run either suppressed OR unsuppressed with some fiddling with the gas system needed for the gun to operate reliably when pulling or installing a can. The new, tappet-based system makes it easy to switch between can or no-can operation.
We'll be tracking the release of the MCX and hope to have more details on the short stroke push rod operating system as Sig shares them.
Rob Curtis writes for the Military Times http://blogs.militarytimes.com/gearscout/.