[bsterns]

Cariboo, I loaded up the maximum #13 Speer reloading manual's RL-19 compressed load of 61gr. with the Sierra 250gr. BTSPs. I shot 6 into a 7/8" group. The group was a near perfect circle. The case showed no signs of pressure except for a flattened primer. No raised edge on the primer firing pin mark. That is really accurate for my hunting purposes. I believe I will keep that load. I used necked up 30-06 winchester cases with Remington 9 1/2 large rifle primers.
Using the data from the Speer's manual for 338-06, 250gr. the muz. vel. is 2531 fps with 61gr. RL-19. The data for 338 win. mag. 250gr. shows a muz. vel. of 2664 using 72gr. of RL 19. That is a lot of extra recoil from an increase from 61gr. to 72gr. of powder.
Using the Sierra bullet in the 338-06 and Speer's GrandSlam in the 338 Win. Mag. I compared the two trajectories and overall performance short of expandability. I put the data into the ballistics program on RealGuns.com. One remarkable thing is that the trajectory out to 300 yds is only about half an inch difference in a 5 inch channel (2.4" high at 100 yds) and virtually no difference out to 225 yds. The even more remarkable difference is that the Sierra bullet from the 338-06 due to its greater ballistic coefficient, though slower, has slightly higher velocity and higher ft-lbs of energy at 300yds than the GrandSlam bullet from the 338 winchester magnum.