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When you’re quieting down a semi-automatic firearm, most of the residual sound is going to come from the action itself. You’ve got a hunk of metal sliding back and forth, banging against other metal bits and venting gasses — you bet it’s going to be heard. The solution used to be to turn the gas system off at the gas block, but Innovative Arms had a better idea…

Switchblock gas systems are traditionally actioned on the gas block itself: There’s a little mechanical switch the shooter moves to turn the gas on or off. But that requires the shooter to move out of position to activate the button, which could be a problem if you’ve already lined up that perfect shot. Gas blocks also tend to get hot, making the switch painful to touch.

Innovative Arms has come up with a better idea: Turn the gas system off at the upper receiver.

By putting the cutoff switch on the upper, the shooter no longer needs to move out of position to operate it, and the switch itself will not be nearly as hot as if it were directly on the barrel. It also means the switch can be larger and easier to operate, and the design allows the shooter to tell with a single touch whether the gas system is on or off without needing to visually inspect it.

It’s an ingenious solution to the switchblock problem, but it does mean that you need a special gas tube to handle the pressure. At the moment they only offer carbine length systems, but they say they’ll be expanding into other lengths as well shortly.

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  1. Does having the block turned on mean you cycle the rifle manually? I suppose if you valued stealth over semi-automatic that would be a good thing.

    • Yup. When you fire with the gas system blocked, the bolt does not move. Keeps the action clean too since you’re not dumping dirty, hot gases into the receiver. If you’re just bench shooting for accuracy with your AR, it will save you some cleanup time when you’re done. The stealth benefits increase also: it won’t eject the shell automatically, and the ejection port will not open either. Probably a really cool technique for use with a suppressor for maximum stealthiness.

      Since the block is on the receiver in this case, the pressure will probably blow up your gas tube – hence the need for a “special” tube. If the block is in the gas block unit itself, the tube receives no gas as all, but the block get HOT!

      I always wanted to see a gas block that had a knob that redirects the normal flow of gas to the tube upward. This would shoot the gas straight up instead of just blocking and trapping it. I wonder if it would affect the bullet speed too much. I also wonder what the anti-recoil affect would be like since it would just push the muzzle down. Doesn’t matter from the bench but offhand shooting might be cool. I may never know ’cause I don’t think it exists (probably for a good reason, I suppose). Oh well. This is a nice option at least.

      • This information and the information you posted above is INCORRECT.

        The switch does not turn the gas off, it reduces the amount of gas that is allowed to pass through, since less gas is required when running suppressed.

        The bolt DOES cycle and chamber a new round. Recoil is also greatly reduced. I have a video on Youtube of me running my WAR in suppressed mode.

  2. FNs have a field-adjustable gas block, but after a few shots it’s too hot to handle without asbestos gloves. Not sure anybody ever tried to suppress an FN, but there’s always some clown ready to try anything. Like Red Jacket.

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