Hello Boyd
You are correct and I can add more here since I have shot the Weatherbys, the 308 Baer and other Improved Weatherby cartridges.
The case capacity is a tad bit more on the Imp cases but the reason most people shoot them is because they headspace on the sharper shoulder instead of the belt as on the straight Weatherby case.
The accuracy range seems to be 3000 to 3040 FPS in ANY of them including the straight Weatherby when using 30" barrels and 220 gr bullets. They ALL seem to shoot the same powder charge to attain that velocity range too. In reality that would make the straight Weatherby the more "Efficient" (fills the case more with the same powder charge) case to use for target shooting. The difference is the headspace on the 35 to 40 degree shoulders on the Improved case. Some people don't like the venturi (double radius) shoulder that the Weatherby has. I don't mind it though and have not had a problem with case stretching that much.
I swithed back to the straight Weatherby because I don't like fireforming brass first before I use it. To me it's a waste of barrel steel. The least amount of rounds through the barrel will make it last longer. In the longrange hunting game, the Imp case, since it has a bit more powder capacity, can be loaded hotter and some like that feature.
Another thought here, the Imp 30s such as the ones mentioned below can be loaded to the velocities of the 30/378 using the longer barrels and that is an added feature of the Imp case.
Now comparing the 30 Imp to the 30/378, the 30 Imp is a more efficient case which means it will use less powder to attain the same (or nearly the same) velocity using the same bullets as the 30/378. You can also do it with a standard magnum action instead of a custom action with a bolt face of the 378 Weatherby size.
As far as the Record in the 16 1/2 lb class, John Buhay did shoot a 10 shot -- 100 Score (the record) with 5Xs and it was done with a 5.3" group. The Group was not the record only the score.
He did it with a 300 RUM and he is the ONLY person I know of that has got that cartridge to work out of many who have tried and given up on it. The reason is the POOR brass available and even John said, he has to go through about 100 cases to get 10 that match good enough to use them. When some of the brass companys like Norma and others produce that case , it will be better accepted for match shooting. Until then it's the straight 300 Weatherby, the 30 IMP such as the 308 Baer, 30 Goodling, 30 Hart and the 6.5/284 that seems to end up near the top at Williamsport every year.
Hope that helped out a bit.
DC
[ 10-15-2001: Message edited by: Darryl Cassel ]
