You're using to much powder over kill. A simple way to figure your powder is to take 240 divide by 2.5 = 96 so you could round this up to 100. This will work good for any bullet weight take the weight of the bullet and divide by 2.5. If your using 150 grain of powder you could easily shoot a bullet that weighs 375. Hope this helps, I also use a 240 xtp and I only use 90 grain of powder haven't missed a deer yet.