I am building a new predator hunting rifle and it will have an 18" barrel shooting light 58-75gr projectiles. It will be ran with a suppressor. I was going to chamber it in 6 Creedmoor but also considering 6xc and 6 GT. I started wondering if I would be losing much velocity with going to a 6GT over a 6 Creedmoor in that short of a barrel. Would the extra case capacity of the Creedmoor gain me anything over the GT with such a short barrel and light projectiles? Does anyone shoot a combination like this? If so what are your velocities?