Personally 9,3x62 but you can see a 8x57, .308W and similar as well (point is in slow heavy bullets from short barrel) - all in all rifle has to be short, light, reliable and expendable - attaching rifle sling at the top of the barrel is a good thing (helps when going through some thick stuff - one of the main assets that got me a R93 offroad tracker:

But you can see many M98 type "choppers" in the hands of other guys.