Does the gas operation of the gun only unlock the bolt, or do they impart enough force to the carrier/whatever to actually force it all the way to the rear?  

Most guns unlock within the first 1/2" of carrier movement, but is there enough force inparted by the gas system to cycle the bolt fully to the rear, or just enough to unlock the bolt and resudual gass pushing on the cartridge force the bolt the rest of the way back?

If it is the former, it seems like there would be alot of force needed to get a short stroke system, and thus alot of wear/tear/smacking around involved in the process.

Short stroke uses significantly less of the gas pressure to operate and improves bolt life dramatically.

I beleive they exert enough force to unlock the bolt, and send the carrier patly back, inertia completes he cycle.  Tak and AK for example, the gas bleed ports are about 1 inch past the gas block.  The other 6 inches of gas tube is a dustcover for the piston.  

Also somewhat like that on FAL, an STG gas tube ends about 3 inches past the block,

Well, if there wasn't enough force to completely cycle the bolt all the way back, then the weapon simply wouldn't work, would it?  

In gas-operated firearms, the carrier gets launched rearward by the gas system, and when it unlocks it pulls the bolt and casing with it--the empty casing does not blow out of the chamber on its own.  That's why torn rims can be a problem if the casing gets stuck in the chamber during extraction--the bolt tries to yank the casing out, and if the casing doesn't want to budge, the extractor yanks off part of the rim instead.

Quoted: In gas-operated firearms, the carrier gets launched rearward by the gas system, and when it unlocks it pulls the bolt and casing with it--the empty casing does not blow out of the chamber on its own.  That's why torn rims can be a problem if the casing gets stuck in the chamber during extraction--the bolt tries to yank the casing out, and if the casing doesn't want to budge, the extractor yanks off part of the rim instead.

Althought don't fluted chambers like the G3's try and solve the problem by "floating" the empty case out of the chamber with rearward moving gasses?

The roller block rifles, AKA, G3, are blowback rifles.

The flutes in the H&K chamber are there to allow the rifle to operate while dirty. Any blowback firearm gets filthy in a hurry and the flutes give the powder somewhere to go. There is some assistance to the extraction process, but it's not the primary function.

Quoted: Althought don't fluted chambers like the G3's try and solve the problem by "floating" the empty case out of the chamber with rearward moving gasses?

There are some larger gas-operated guns which are in effect 'gas-unlocked blowback' hybrids: the gas operation only unlocks the action, blowback does the rest. One of the first of these was the WW2 20mm Hispano aircraft gun and some current Oerlikon cannon still use this system.

In fact, in a very fast-firing linear-action automatic gun (whether gas or recoil operated) the breech opens while there is still a lot of gas pressure in the barrel so blowback forms an important part of the operating mechanism. I don't know of any small arms to which that applies, though:  the retarded blowbacks like the G3 / CETME and various French weapons use a different principle.

Tony Williams: Military gun and ammunition website and discussion forum