Thanks for this good info which reassures me I am on the right track. I took my rifle to our range which runs to 800 yards here and using my chronograph, which has set in a bag for twelve years, found that starting loads of 86 grains of H1000 gave me 3,124 fps. I have an old Krieger 29 inch barrel that I used formerly for long range benchrest and it now has a Vais muzzlebrake. At the first shot with this humungous cartridge all the cattle feeding along side the target range disappeared into the junipers.
I increased the loads and found the velocity jumps were consistent. At 95 grains I noted very flat primers and 3,425 fps . 96 gave me the ejector impression on the base and that is where I stopped and will be using 95 from now on. It was 87 degrees when shooting so cooler temperatures will allowa larger margin of safety.
I formerly had this barrel chambered in a wildcat of my design using RWS brass and it was very efficient, achieving Weatherby like published ballistics. I replaced my old brass with new RWS brass and it is much inferior. Thus the conversion to the 300 RUM.
MY hunt does not start until late October and I look forward to shooting this on the range and getting to know much more about trajectory and wind drift. Thus, if I do take a 800 yard shot the chances for success will be enhanced. I hope I do not have to do it.
I attended the PLR-1 Long range school at Whittington, NM and we ended up shooting in hunting terrain as far as 1,280 yards and I did manage to hit that 12 x 15 steel plate 3 times in a row at the distance with my 6.5 x 284. I also noted the wind drift exceeded 8 feet and was fortunate to find a white rock in the embankment that worked perfectly as an aiming point. I noted the 300 magnums, when they did finally manage to hit that plate really moved it around. This was shooting of course, and not real hunting, when first shot accuracy is totally necessary.
Thank you for your information,