Yep,Michael is correct. The tables only give a hint,loads must be grouped and confirmed in the real world ,no matter what chronographs or tables one is using at 100 yds. Holding over is not the best way to go,one is better off by adjusting the scope to the (hopefully) known distance.
This is from a 257 Weatherby page,by Chuck Hawks:
In addition to Weatherby, Federal Cartridge also loads for the .257 Magnum. Federal offers two Premium loads, both with 115 grain bullets at a MV of 3150 fps and ME of 2535 ft. lbs. One is a Nosler Partition bullet, and the other is a Trophy Bonded Bear Claw bullet. At 300 yards the velocity of the Nosler bullet is 2440 fps and the remaining energy is 1515 ft. lbs. At the same distance the Trophy Bonded bullet is traveling at 2400 fps and retains 1470 ft. lbs. of energy. The trajectory of both bullets is very similar, with the Nosler bullet shooting just slightly flatter due to its somewhat superior ballistic coefficient of .389. The trajectory of that bullet looks like this: +3" at 100 yards, +3.3" at 200 yards, +1.7" at 250 yards, -1.2" at 300 yards, -5.5" at 350 yards, and -11.5" at 400 yards. With this load the .257 Weatherby has about a 335 yard point blank range on medium size big game animals.
I played around with "Ballistic Basics Pro". Assuming the real velocity was not 3150 but 3000 fps for whatever reason and exactly 3" high at 100 yds the drop at 380 would be 11-12"... just an example. What kind of velocities are you getting? And how does it group at 100, the group size is at least four times that at 400, adding more error? Are you absolutely sure you missed high,not low? That distance is where it starts to drop fast,20 yards more and the drop is 13". What if it was closer to 400 yds after all?
Or what if the distance was only 340 yds? Then,with the MV being 3150 fps, 3" high at 100 the drop is only 4" at 340... easy to shoot too high when the group size variable takes it high another three inches,for example. Just theory here,you had a question mark in the "385?" yards.
Looks like I have some extra time now... please don´t get my "what if:s" wrong,trying to be helpful here,waiting for the mailman to bring some bullets...and of course: Welcome to the forum and congrats for the buck!
EDIT: Also,if your scope is mounted very high (2" center-to-center) the drop becomes even less in the 340 yds scenario, only about 3". I know,only one inch less but if your rifle shoots 1 MOA it may take it high another 4"... Endlessly variables in this game, that´s why I like it.
Where is the mailman?
[ 10-16-2003: Message edited by: Petander ]