Saying "a couple of people" was probably hyperbole. There has been at least one documented case, however, in which an elderly woman was killed by a heavily upgraded (now defunct) Digicon airsoft gun. They were overly powerful stock and were marketed more as target guns to the japanese crowd rather than skirmish pieces. Currently Japan has a .98 joule power limit on airsoft guns, comparable to the 1 joule power limit in place in the UK, which brings them down to safe velocities even at point-blank ranges. I'm not sure whether this power limit was implemented before or after the woman was killed, but I want to say it was a reaction to her death. That was an exceedingly rare case in which the gun was pushed to past-pellet-rifle power at what I can only assume was close range and a fairly fragile victim, but it has happened at least once. I still hold that they are, within reasonable velocity ranges, far safer than simunitions or even paintball under normal conditions with normal safety precautions.
The Hamas conversion is, as far as I'm aware, total BS. As a general rule, airsoft guns have to be built to slightly different dimensions than their real counterparts to fit the gearboxes that drive them. There are aftermarket and stock metal receivers for them available, but even those have different specs than would be usable for an actual firearm. The only exception to that rule that comes to mind is the newer gas blowback m4 style rifles whose lower receivers were *almost* in exact spec; close enough to be feasibly converted with a bit of machine work. At the same time, the cost of one of these (very high end equipment, running in at least the 400+ range) offsets any practicality of even attempting a conversion since you're effectively paying $400 for just a lower receiver that still needs machine work. In a country in which the other parts are available, the lower receiver is probably going to be available as well, and it would be incredibly hard to justify paying $400+ for just an *almost* working lower receiver.
As far as I know, none of these guns have ever been converted; though, the BATFE did confiscate some of them because they had select fire parts in them and the potential was there. Past that, I've never heard of or come into contact with an airsoft gun that could be converted. Low-to-mid end metal parts are pot metal, and even high end you're dealing more with aluminum than steel. Add that to the high price compared to current marketed units or smuggled-in items, the differing dimensions, and the fact that if you know how to machine well enough to make a conversion work then you've got enough machining skill to build a gun from scratch anyway, and I simply don't buy it.
