[Marwan]

it is doable and as long as travelling with a speargun is legal in your country i dont think it should be a problem, in some countries that dont allow it, i would not recommend this as it could be misunderstood as a deliberate act of trying to do smeting wrong, but what you say seems fine...in terms of how you do it:
1- you will need to unscrew he 2 little screws on the rear of the gun just in front of the handle (the ones that hold the little plastic line holders with the crocodile teeth in place)
2 - push the sleeve with the iline guide forward, exposing the metal pin, holding the handle to the barrel..
3 - get a very thin screwdriver and gently hammer the pin out
4- pull the handle out (the handle could be a bit sticky to the barrel still), try hammering gently (but wrap with a towel to avoid damage) or leave in hot water a bit to make it easier..