In Italy we have the traditional wild boar driven hunt especially in Maremma(The south part of Tuscany), where it is born we have to shoot at very close range 99% of shots under 20 meters the animals arrive against the hunters very fast and full of adrenaline and testosterone and the shoot placement often isn't good.
In these conditions someone use double rifle, also me, the most common cartridges for double are 8x57irs and the 9,3x74R.
The 8mm is use by who prefer a more handle and lightweight double while 9,3 for who prefer the maximum stopping power.
About cartridge I will start from 196 grains for the 8mm and for 9,3 from 232 or 286-293 grains choose from the zero cartridge of the rifle.
About 9,3 bullets in driven hunt if you need info ask, I have tried some of them in driven hunt.
My suggestion for moose and wild boar is 9,3x74r with soft point bullets in a classic German double rifle but if you prefer something more light go to 8x57jrs.