Mechanicals dont necessarily open because of the speed of the crossbow,most crossbows are not as fast as a manycompound bows. There are 5 of us that hunt together during Bow season and 3 of them have faster bows than my Horton, which is rated to shoot at 305 fps. (I have never chrono'd it, but if we all shoot at the same time the other three hit before I do)

I shoot Spitfires and have never had a problem with them. I have never shot a turkey with one, but for deer they work very well indeed.