KcTbear,
I'll give you a starting point on loads for your .300 win mag. The first powder to start with is REL 22. That's probably, of course it's debatable, THE powder for a .300 win mag and 180 grain bullets. 75 to 76 grains is most often THE most accurate load based on my endless reading on the subject.
My best load, in MY rifle, has been 75.5 grains with a 180 gr Nosler Partition, WW brass that's PFLR sized to fit my chamber and a COAL of 3.360".
You'll get many other opinions about THE load for a .300 win mag, but this is as close as it gets to a go to load.
I agree with FH and that is what I have used in the 300 Win mag as a very good place to start with a 300 WM.
Also agree regarding the longish throats and why factories do it.That said it has caused me some issues in M70 Classics.I have seen some accuracy issues with lighter bullets. The 180's and up seem to jump the distance and shoot well;in some rifles 165's did not do so well.This issue of making a jump to the lands is no big deal if the throat is cut with a good reamer IME but factory dimensions of the throat can be a bit sloppy....some will shoot and some won't.
Also deep seating can cause tension issues with SOME bullets in the short necks of a 300 WM.
The solution for the M70's was to change out the mag box,follower,ejector,etc for 300 H&H-length.This allowed seatin closer to the lands(not too close!) and just made life easier.I figure if you can have the magazine length you might as well get it and use it.
