As it may well be viable to use standard .303 174gn load data for the .303-270 (probably 130gn bullets) I've been looking through some old manuals.
1967 Edition of Hornady's Handbook doesn't list W748 or W760 loads for the .303 at all. They do suggest the Hornady 150gn SP is the best bullet for hunting in the .303 out to 250yd.
The 1985 Edition does list W760 down to 150gn bullets (42.5gn up to 50.0gn max under the 150gn bullet), they also suggest loading short of these levels to increase brass life.
- Screenshot 2022-11-16 204751.jpg (92.65 KiB) Viewed 1895 times
Lee's Modern Reloading 2nd Edition 2009 lists W760 down to 125gn jacketed bullets in the .303 at 45.0gn up to 49.0gn max, 43.1gn up to 49.0gn max with 130gn bullets, 44.0gn to 48.0gn max with 150gn bullets - this is 2gn below the Hornady data.
Speer's 12th Edition 1995 for the .303 lists H760 down to 100gn bullets and notes you should use magnum primers with W748 and W760. Charges are 47.0gn up to 51.0gn max with 100gn and 125gn bullets, 44.0gn to 48.0gn with 150gn bullets.
Lyman's 44th 1967 for .303 doesn't list W760 either - apparently H414 didn't arrive until 1967, 760BR in 1968, and W760 not until 1973.
Lyman's 48th 2004 for .303 lists W760 down to 150gn bullets - 43.0gn up to 48.0gn max.
Interestingly Lyman's 1967 data for 174gn bullets on AR2206H/H4895 at 3.075" was 39gn making 2207fps up to 43gn max making 2469fps (with 42.5gn duplicating "factory" loads), but in 2004 is down to 37gn at 2032fps to 41gn at 2341fps at 2.945" - I'm running 38gn at 3.030" making 2300fps.
I have got an old Nick Harvey manual that I bought when I was chasing W748 .303 data but it came long after we started shooting it so I didn't need it, if I can find it, and it has any .303-270 data I'll add it here.