I picked up a Yugo 59/66 at the Big E today (yes, I could have got it for half the price 3 or 4 years ago, but there it was, and there I was ... ). So now I'm looking at this wacky grenate launcher thing, and there's a gas shut-off valve. It looks like an inverted "L" with three positions. From what I can gather the center position is "gas off". Depress the button and slide right and you're in "Semi-Auto" mode. Slide down and your in "Grenade Launch" mode. Here's a photo from surplusrifle.com: What I'm finding is that the button does not slide down to the grenade mode. Might this feature have been disabled to prevent the actual use of the grenade launcher? I haven't read of this and, if so, I'll be mightily disappointed.