In the UK the only components that we could get when 303 was still used for "hunting" were the Norma or Speer bullets. Neither Winchester nor Remington soft-point bullets were imported as components although one could get Winchester and Remington unprimed cases!

For reloading I used to use 41.50 grains of VV N140 with a 174/180 grain bullet. This duplicated the sight settings on military SMLE and No4 rifles and shot to same POA as issued military FMJ Ball. I had tried 42.00 grains and found that the extra half grain made no difference at all excpet to use up more powder!

I also tried 41.00 grains of VV N150 (same volume as 42.00 grains of VV N140 so no need to change powder measure set up). This gave less apparent pressure and less apparent velocity than N140. I then tried 42.00 grains of N150 and this did match POA to the military sight settings. BUT as it was that "half grain" more and no better than the N140 I did not persist with it.

I've also used H-4350 and H-4895. I could not match factory performance using H-4895 in any load that was not stiff to open with bolt "hard back" on locking lugs using H-4895 and do not think that it is possible to equal factory velocity in 303 with the 174/180 grain bullet with a safe load of H-4895.

I also gave up H-4350 after testing 43.00, 44.00 and 44.50 grain loads with the 174/180 grain bullet as I could not get a POA match between it and factory ammunition. I did not go higher with the powder charges.

The problem with 303 is that it is a relatively small case capacity and is pretty much 100% filled to be able to match factory loadings.

Personally? I think that the Germans had the better choice with the rimmed 7x57 and rimmed 8x57 cartridges! Or if you want a traditional and effective British rimmed cartridge go to the 300 H & H rimmed.