Free Floating barrel

Free floating has it's advantages and disadvantages over fixed barrels.

Free floating barrels barely suffer from temperature changes and pressure changes in the airtube/bottle (yes the air tube flexes a little while the pressure is changing). The disadvantage is indeed that there is a POI change possible when you slam the barrel (although you would need to bump it hard before that happens).

Fixed barrels have the opposite advantage and disadvantage: more rigid due to the extra support from the air tube/bottle but suffer from temperature changes and pressure changes in the tube/bottle.

Sometimes there is a mix of both, that there is a brace around the airtube and barrel but the barrel is supported in an oring inside the brace. This reduces the movement of the barrel that's possible when bumping and decreases the effects of temperature and pressure drop.