JP straight from the 2010 Hodgdon powder website (they make/sell Win powders now).
http://www.hodgdon.com/basic-manual-inquiry.html300 Win Mag:
180 GR. SPR MT-SP Winchester 760 .308" 3.285" 58.0 2722 48,200 CUP 62.0 2845 52,300 CUP
The bullet in this case is the Speer Mag Tip. I don't think its enough different from the Rem CorLokt to worry about at the starting loads. Both are standard cup and core bullets. The mag tip might have a little bit harder lead in it. I'd say your Barnes data is a little bit hot to start with compared to this data. And Barnes X bullets are much harder - less comparable to the Speer.
Like Scatter says, 760 is probably not the prime powder for the 300 win mag. My old Winchester Western Ball POwder Load manual dated 1978 does not list 760 for the 300 win mag. Slower powders like IMR 4831, H4831, H450, H1000, Reloader 19 and 22, 25 are probably better. If 760 is all ya got, it will work.
Even with Hodgdon, 760 is the last recommended powder for 180 gr bullets in 300 win mag.
Demented: The cor-lokt is one of the better cup & core bullets for holding together but at very close range and full power 7mm mag loads I think you better expect pretty explosive performance. I'd prefer a more premium bullet like the bonded jackets, partitions or X bullets. Or if you will only shoot at close range, don't load to full power. Load a 7x57 or 280 equivalent velocities.