I cast and powdercoat for all my guns including my .270 Win. Treeman will be able to give you the answer on what sort of velocities he achieved without leading but my understanding is that inside of 2500fps powder coated and gas checked bullets are OK. I haven't taken mine that high but at 2000 I experienced no leading and very nice accuracy from one of the three bullets (a very old Lyman on the left) i experimented with.

You do not need a gas check with PC bullets. I have to date never shot a lead cast bullet from a rifle in rifle caliber, only in pistol calibers. The forums I read on also claim 2500 fps are achievable without leading ? Most shooters seem to limit themselves to 2200-2300fps.
I have only just skirted the 2000 fps mark.

Once I find a .303 mold in .314 size I will test higher velocities.

To test those 303 bullets, use S335. Lee's Reloading Manual has a formula that calculates a charge if you input a speed that you wish to achieve. Ds J, I will send you photos if you do not have that manual. Just let me know.

You do not need a gas check with PC bullets. I have to date never shot a lead cast bullet from a rifle in rifle caliber, only in pistol calibers.

I think this may be a bold statement especially wrt to rifle bullets. I hope it's true but I doubt it's an absolute. 

To test those 303 bullets, use S335. Lee's Reloading Manual has a formula that calculates a charge if you input a speed that you wish to achieve. Ds J, I will send you photos if you do not have that manual. Just let me know.

Thanks, I will check once I am home and let you know if necessary.