First let me say, I am a die hard muzzy fan and love their product, but I have to get this out. I purchased the new mx-4 100gr AND BEGAN TO SHOOT THEM. Excellent groups flew great. Now here's the kicker, after about 20 shots with an actual sharp head, not the practice blades. The heads began to chip and break and the blades began to move left and right towards the bottom of the ferrule, even after I tighten them up. This is quite dissapointing considering they are the toughest heads on the market. So I went out and bought another pack and the same thing happened. Just wanted to let folks know that these heads are not as tough as the muzzy's of old.