.458 brass grows when fired and resized like any other caliber. If the chamber is tight and die is a close match, doesn’t grow much. Chamber sloppy and die is something else, it grows. Remember the the Rcbs X die? It attempted to hold the length static while resizing. It disappeared so the market said it didn’t work. I never used one. The idea had merit though. As a side note, you maybe are trimming needlessly. Certainly are in a Lott chamber but many 458wm will accept brass longer than spec.
That is certainly a good point on not needing to trim for the Lott chamber. My thought was to just use WM spec ammo in all guns. Not only for compatibility in different guns, but also to avoid having to trim to different lengths, adjust seating dies and crimp...Also, after this first firing, maybe it won't grow as much, who knows?
I will hopefully get some velocity data on these loads later today, or tomorrow, as well as measuring (as well as I can) the throat of the Lott.
