Sorry (but not sorry) but I don't have a 400. I have a 500 (.25) & a Boss (.30). Same platform. Unbelievable guns, so much so that I sold all my others & only own those two. In the words of Centercut to me "It's the best platform FX has ever made. No FX guns are more accurate than these". I've never found either one to be "very sensitive" to different holds & both have been TROUBLE FREE since day one. I assume the 400 would be the same. They won't shoot slugs due to the Original Smooth Twist barrel but it doesn't matter to me. I can routinely make 100 + yard shots with confidence or I should say the guns can if I'm doing my part. Hope you get it, you'll love it!