My guess, since its British, it was meant for the Sterlings. It would probably be fine in any of the heavier built and barreled guns as well.
With what the MP5's and some of the others go for these days, its not worth it. It wasnt worth it when they were $800 either.
Realistically, its not really worth it in any of them if theres a chance at all something might go wrong. Whats the point? Theres plenty of reasonably priced and reliable ammo out there that wont mess up your gun.
I personally wouldnt shoot any of the SMG stuff out of one of my handguns, but if youre up to it, have at it. I already learned my lesson.
