Hi I took immediately 2 ranks of scrounger perk in order to feed my laser pistol with fusion cells when I get the pistol. Till now I don't use the pistol and I am saving up ammo. However the game loads me especially with .38 and .50 cal and maybe .45. However I almost never find fusion cells or other interesting ammo. Is it because I am still wandering in the north ? Is it because of my level or whatever thing I don't know.

I am just coming to a conclusion that this perk is useful only if you are going to use 50 cal ammo.

That perk adds additional stacks of ammo in ammo crates and sometimes other containers. It doesn't influence the drop chance of rarer ammo.

Does luck alone influence ammo find ? especially rare ammo find ?

Some sources claim there is minimum level requirements for certain ammo types to spawn to random containers. Before that you supposedly can only find the ones that are scattered in the world space. For fusion cells this minimum leven is said to be 7.

I've got absolutely LOADS of fusion ammo no (level 59). What I am short of is shotgun ammo. It's random but linked to your scrounger and level I think. I do know I am picking up crazy amounts of 38 (I have around 10k of that IIIRC).

Ammo drops seem level dependent to me, the more levels I've got the more ammo types I've been finding.

If you're farther to the north and still at a lower level, you won't be finding fusion cells very much. I'm level 36 now, and since level 20 or so I've accumulated several thousand fusion cells. There's no shortage of it. You have to reach a certain level and a certain point in the game before you really start getting a lot of it.

I have thousands of rounds, and I don't even use energy weapons ever. I'm still holding onto my .50 cal sniper rifle, fully modded combat rifle, and fully modded advanced combat shotgun. I need to play around with the energy weapons a little more.

Do you have the scrounger perk ?

I think, as it has been said, that it affects the quantity of ammo that shows up, not the variety of ammo types. Given that you say you're still exploring the north area of the map that seems to indicate that this is the case.

Although mid to end game I think that its more convenient to farm weapon shops you set up in your settlements, as well as some non settlement traders who i've seen always have above a hundred rounds for most of the primary ammo types.

just as in FO3 I find my self challenged to get enough .44 rounds, even though this time its not one of the more powerful gun types.

Scrounger perk does not give all ammo types: http://www.nexusmods.com/fallout4/mods/3624/?