I'ts been around for a few years now. $270 for AR, $200 for AK version at Cabelas. It would be fun a couple of times, but even with the cheap ammo I shoot it would still be a waste/novelty.
just a gimmick you'd never see on a serious rifle. spend the money on a trigger and shoot damn near as fast and a hell of a lot more accurate (unless you're shooting a trunk lid at 3 yards).
I picked one up a couple years ago just to see if it was a gimmick or the real deal. Turns out it's a little bit of both.
That was a 100-rd mag dump with the Slide-Fire stock and a cheap-o KCI drum. No jams, rifle was very easy to control...I was just spraying all over the place for the hell of it. Rate of fire slows down with the heavy mags...30 rounders empty much faster. If you want to turn heads at the range and have $ to burn on ammo, I think you'd have a blast with this.
BUT...
Fat chance of shooting your rifle with any sort of precision in "single-shot" mode with this stock on there. The pin that locks it into position on the buffer tube does not do a good job of staying in place during recoil, so the stock moves around a bit and affects your trigger mechanics for follow-up shots. Also, if you have an over-sized trigger guard, the stock won't fit all the way onto your rifle. Finally, the stock is not adjustable to your build, which is a bummer if you're a bigger guy, or prefer greater length of pull. I don't see a sling adapter on mine, either.
In the end, it's a ton of fun if you're just out plinking with your buddies. But I would NEVER, EVER use this stock in an actual firefight.
And don't pay full price for it, either...it's just an injection-molded polymer novelty.