Had a chance to shoot a few rounds this morning over the chronograph. I had loaded three different amounts of 4064 behind the 200 gr Hornady in the newly fire-formed cases. Below is the average for each load (five shot strings).
57 gr. 2455, 58 gr. 2515, 59 gr. 2565. The 59 gr load is still 1.4 gr less than J D's maximum. I was particularly impressed with the 58 gr load. Maximum difference in velocity over the 5 shots was 9 fps. However, the proof will come when I start looking for accuracy.
For purposes of comparison the load that I like (not really max) for my 338 JDJ#2 averages 2369 with that same bullet. I also chronographed the Freedom Arms 338 Federal with two different factory rounds. The Federal Vital Shock (210 gr partition) averaged 2392. The Federal 200 gr Uni Cor averaged 2486.
Hope this information is useful to someone.
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It's more important where you hit 'em, than what you hit 'em with.