Near as i can tell, from my data of measured speeds; the speed of a 300g Gold Dot pushed by 105g BH is 1795 fps from my X7, and 1855 fps from my Triumph and Accura. I believe the X7 has a 24" barrel, and the Triumph has a 28" barrel; the Accura has a 27" barrel. So, it seems the loss/gain of 4" of barrel is aboout 60 fps.