I've tried four different powders with 180g Nosler Accubonds and it is the best so far. Problem is that I can't get a straight answer from Ramshot. I pointed out what I believe is a mistake in their load data, had likely confirmation from Nosler and get a nonsense answer.

Here's the details...max per Ramshot with 180 Nosler Balistic Tip is 86.0 g. Max with 180 Partition is 83.6 g. I asked them if I could use the BT info for the Accubond and was told, "no, you need to use the Partition data". So, I load to 84.0g with no sign of pressure whatsoever. At this point, I noticed their data for the 200g Partition is 84.4g of Magnum. Nosler agreed this "sounds backward". I contacted Ramshot again to point out the issue and was told, "just load to our velocity and you'll match the max pressure". No questions about barrel length, seating depth, etc. Does this sound right to you?!?!

Regardless, At 82g, Magnum is always .5 to .7 MOA in my rifle but I suspect there is a sweet spot closer to the true max load that will get me over 3000fps.

I'm stumped. Anybody use this powder and willing to share your experience and/or wisdom?    

I have a bunch of Magnum for my 300.  One thing Magnum has always shown for me is awesome velocity with no pressure.  I can not remember my question exactly but I had something similar I asked the folks at Sierra.  All I can recommend is start mid-range, load up and look for pressure.  Accuracy has always been good.  Not great but good.  Plenty good for hunting purposes.  I am running from memory here because it has been quite a while since testing but I know I was at least 2 grains over max with several loads when accuracy started to wander and no pressure sign what so ever.  I think Magnum is a great powder but my go to has always been R22

Any testing you do, please update with results.

Tested with Magnum and RL26 since last post.  This makes five powders and Magnum is by far the best.  I'm beating factory published velocity by about 50fps at 2g under max.  No pressure whatsoever.  It groups about an inch +/- in my box stock Model 70.  This is the load I've settled on and will be tweaking COAL to see if I can squeeze a little more out of it.  To save folks some trouble, here is my review of RL 26 from another thread on another forum:

"As a follow up to my testing with RL 26 in my 300 WM, all loads to max produced about the same 2 1/2" to 4" groups. It also smoked like I was using Unique and seemed fairly dirty on cleaning. I spoke with Alliant and was told it is "SOMEWHAT" temperature insensitive...literally told that "sometimes it is and sometimes it isn't". From what I gathered, it is more insensitive to cold than heat but no promises. Also, I did not see any less copper coming out of the barrel on cleaning. Seemed about the same as everything else. It may produce a little more velocity but I didn't chronograph it based on the above results".