Without wishing to be unduly pedantic, I am presuming that what you actually want to know, is the name of my favourite cartridge?
So let’s first define what we really mean by ‘calibre’ and ‘cartridge.’
Calibre is the diameter of the bore of a rifle before the rifling is cut or hammered in.
Thus, all cartridges from the little .30 Carbine to the .30/.378 Wetherby Magnum are .30 calibre and use bullets which are .308 in diameter so they fit right to the bottom of the rifling grooves.
Definitions within the calibre are the name of the cartridge.
With that out of the way, my own favourite cartridge would depend on whether I needed one for shooting at relatively long range on the hills of Scotland and the wide fields of east Anglia or whether my stalking was only in woodlands and fields where ranges would not exceed about 175 yards.
For the former I would stick with my .270 Winchester. It is often maligned – largely by people who don’t know what they are talking about – but is in fact just as good as any of its more modern competitors.
If you do fancy something a little more up to date, then the search can begin and end with a 7mm Remington Magnum.
Back in my favourite woods, there are two cartridges that have given me more pleasure and satisfaction than any others.
The first is the .30-30 Winchester which is most commonly found in those little lever action rifles which are such a delight to use in the woods.
Mine was a single shot model and it was capable of knocking down a Fallow buck at 170 yards, which was the furthest I ever needed to shoot with it.
If you fancy a bigger, heavier bullet for woodland deer, then my other favourite – also brilliant for Wild Boar and in the African Bushveldt – is the .358 Winchester.
I am delighted to learn it is again available chambered in Browning’s excellent BLR, lever action rifle, if only my pension would run to such things.