Out of the box, the DPMS 308 Rifle is a platform that can be configured either for precision tactical or competition target use if you consider a precision tactical rifle to be something that a marine scout / sniper would carry. The same ability holds true for the Armalite AR10T, Knight SR25 and Tubb2000.

Take a look at the following web location for the Tubb2000 and compare the tactical and competition versions and you will see how little difference there is.  The Tubb2000 Long Range Model really illustates that there is not much difference between a precision tactical rifle and a long range competition rifle.

http://www.mcbrosrifles.com/tubb_2000.htm

Honestly, the only competition rifles that are probably not ones that you would lug around in the sticks would be precision Benchrest  or Olympic / International rifles and that would be because those are so precisily tuned.

As far as barrel length, 24 inches would be considered neither long or short for a rifle.   A long barrel would be considered 26-32 inches and that still wouldnt make it unsuitable for tactical use.  For example, my SAKO TRG42 .338 Lapua Magnum has a 27.5 inch barrel and that rifle is used by military sniper teams around the world.

http://www.sako.fi