Had same problem BEFORE I went to high FOC arrows with 2" blazer vanes. The 4" and 5'' vanes, when combined with low FOC, were rotating the back of the arrow. Currently using Gold Tip Lazer IIs with 110 brass insert, 2" Blazers, 100 g Slick Tricks. Weigh 405 g, 18.5 FOC. Sweeeet!~