They don't shoot right at those numbers. My Beeman P1 shoots 8.6gr Wadcutters at about 520fps.
Beeman's agreement with Weihrauch has meant that they haven't had to worry much about competition in the U.S. until recently. They've been quoting that velocity figure for many years, not just since other firms have started bootlegging the HW45s into the States in decent quantities.
But they may be identical guns--there's even the possibility that the HW45 numbers are intentionally deflated a bit (perhaps by testing with heavier pellets)so they can be sold in more places. I believe Webley used to do that with some of their air pistols.
Rebadging in the airgun world is pretty common. RWS, like Beeman, doesn't actually make any airguns--most of the airguns sold by RWS are made by Diana Airguns. Umarex also makes a lot of CO2 pellet guns sold under various different badges. Some Daisy airguns made by a Turkish company and rebadged, and Crosman has a deal to sell Mendoza airguns (made in Mexico) in the U.S. under the Crosman name. I'd say that if you buy an airgun in the U.S. from anyone other than Benjamin Sheridan, there's a very good chance you got a rebadged product.
If you REALLY want to get confused sometime, try to figure out who makes pellets. There are only a few quality pellet makers in the world, but you can't tell from the brand names on the tins.
Truthfully, the 50fps wouldn't bother me. The variation in individual airguns is probably more than that. You could buy the Beeman and end up with one that wouldn't shoot over 550fps or you could even buy the HW45 and you might end up with one that shoots better than 600 with light pellets. What I would worry about is the possible difficulty in getting it serviced. It's almost certain that Beeman won't honor the warranty--but they might refuse to service them entirely. You could call them and ask if they service Weihrauch guns that don't have Beeman markings.
