However, I am not certain whether a centrefire .22 will be enough to humanely kill even a small deer like a Muntjac. Can you shed any light on the subject?

Stalking

GEORGE WALLACE says:

I certainly can! For several years I stalked roe deer in Scotland with a delightful little CZ mini-Mauser carbine chambered for the .223 Remington.

Light, accurate and easy to handle whether climbing into a high seat or wriggling through thick bush, its 18-inch barrel didn’t prevent it putting down Roe with real authority.

The deer couldn’t tell the difference between Federal’s 55 grain loads or my own handloads using Hornady’s 60-grain round nose bullet.

Interestingly, one of my stalking friends said he reckoned my .223 put down Roe quicker than his .270.

I’ve never shot a Muntjac but based on that experience I don’t think you’ll have any problem killing them cleanly with a .222 or .223 as long as you choose a suitable bullet, ie. not one of the rapidly expanding ‘varmint’ designs.

Bullet placement is more important than calibre or muzzle energy, so just remember to shoot straight!