Rklenke wrote:A "jacket bulge" could be the reason my 250 grain XTP reloads are 200 fps faster than the Hornady book says they should be.
i'm going to assume that this was a typo and you meant 250 FTX. There is no 250gr XTP load data for the 450 bushmaster in either hornady's 9th or 10th - it does not exist for the caliber, likely for the reasons posted in my screenshot above.
plant_one wrote:
if you're discussing the 250 FTX (#45201) and not the 250 XTP (#45200) as for reasons of velocity gains, it could be several reasons - minor bore diameter difference, barrel coatings (Melonite, etc), rifling difference (5R/5P vs traditional cut/button rifling), a tighter chamber, shorter OAL, longer barrel (their data is from a 20" barrel) style/ammount of crimp(s) applied to the brass, neck tension due to cleanliness (or lack there of) or a combination of these things.
without knowing more about your individual firearm and your loads and loading processes, its just something nobody will be able to speculate as to the why on.
if you'd care to share some more data and clarify some things for us - maybe we can pinpoint why you're seeing velocity's exceeding book data by so much.