I've got a PERFECT idea... it worked for me, I'm sure it'll work for you. Okay first... you have to be 17... then, you buy the game. THEN you're done! Oh wait... that didn't help at all >_> Well, the M rated games I've bought before being 17 were done by not mentioning the rating... too late for that, you could always just go and try to buy it, the worst that happen there is the person selling it to you doesn't let you buy it, in which case... you can always go back to plan A
sorry for the non-help >_< I tried...
Hasta Luego
"L"Chupacabras
P.S.: I think maybe you should just hold off on the idea of buying that game, if it'll get your parents mad at you, there's not much of a point now is there? Also, can't you turn off the blood in that game? Give them details! (I love being a hypocrite every once in a while)