I am not having any issues, but curious on some experienced thoughts on what causes noticable pressure changes. Here is a scenario and some thoughts I have, relating to reloading 9 mm. Lets say that I am currently using "x" bullet. With all bullets, I tend to save one in small plastic ziplock and blueprint the bullet to some extent. length, weight, etc. Once I have an established load, this allows me to calculate the internal axial depth from the bottom of the seated bullet, to the internal face of the casing, thus giving me a known internal volume. Let's say that I chose to switch from a Hornady 124gr HP to a Berrys 124gr FP. If I am conscious about insuring I maintain the same internal volume, (provided the subsequent OAL is allowable), can I assume that I would see similar safe pressure situations across both projectiles, or any others for that matter, provided they have a flat base. I could be way off line, but my thought was that if I maintain a consistent internal volume, regardless of bullet, I should see no changes, other than additional pressure from a bullet weight change or change in rifling / bearing contact surface. Does the bullet / rifling amount of contact alter internal pressure significantly? I would never shortcut my reloading practices, or not refer to manuals. I only load for about 6 calibers, but for interchanging pistol bullets, I am curious if my thoughts are sound.