I recently scored a complete set of "Handloader" magazine, in binders, from issue 1 to 156.
I had previously bought the CD ROM version of it and the "Rifle" sister publication.
Anyway, in the July-August 1980 issue is a very useful article on cast bullets and Teflon tape as a lube / "heat shield".
It might be useful if the "gatekeepers" could see if Wolfe Publishing would allow a posting of the complete article here.
To the "meaty bits":
The authors played with bullets loaded into .243Win, .308Win, .30-06, 7 x 57 and .30-30.
Reported results are excellent, with 150grain bullets being successfully driven to 2,615 fps from a .308Win and at 2,820fps from a .30-06. That is fairly steaming for a cast bullet.
The catch is that they used a "Loverin" style bullet that has many narrow "grease-grooves" along the bullet. A gas-check is also used.
"Lee" apparently don't make a Loverin style mould in .312 size, nor do Lyman.
However, Cast Bullet Engineering in Sydney, Australia have several candidates, a couple of 176gn, .310 designs; (310176L and 313176L) and a 190gn model (313190L). The 190 grain job looks like the best prospect.
The CBE site is here: CAST BULLET ENGINEERING - Home
As with a lot of .303 ammo info, you can use the same bullets in your trusty 7.7 Arisaka or 7.65 Mauser