I am reloading for an older '66 Mossberg 800a .308 WIN. My COL is 2.954,seated a on the lands) with this particular bullet. However, the chamber will not allow anything longer than a 2.75. That is a 2 tenths "jump" to the lands and longer jump than I have ever had to leave. Could this be throat erosion, or were these rifles built with larger jumps to the rifling? Factory ammo measures 2.69 and clears the chamber easily. Thanks in advance