So after New Vegas i went back to FO3 to perhaps find out what the "omg f3 is more explorablelike NV r bad : (" trolls are on about.

I did find that the world is more lively than i remembered, although at this point i'm not entirely sure if i enjoy that. There seem to be random mobs littered around every other step. Just making my way from Big Town to Arefu i had to kill one supermutant, a pair of raiders, a vicious dog, a radscorpion and some crab thing that i had to run away from because i ran out of ammo. It seems like every time i defeat something i turn around just to see the next completely unrelated damn mob running towards me. But i digress.

I'm having ammo problems. Considerable ammo problems. Just two minutes ago i had to beat down a supermutant brute with Moira's repellant stick.
I'm a guns character with a 10mm SMG, an assault rifle and a hunting rifle so i don't have to rely on one ammo type. But that doesn't help.

So guys, throw me a bone here, where'd bethesda put all the Guns ammo? Am i supposed to spend the next half a year staring at Moira?

Ammo is sometimes sold by traders, like Moira. It is in places like lockers, metal boxes, safes, and...ammunition boxes.

Always loot the corpses of your fallen enemies. Raiders tend to carry a couple different weapons and ammo.

15 rounds of 5.56 every three days

I was thinking about going to Rivet City to find a better trader but i can't get there with the repellant stick alone.

The traders are unreliable sources, I agree. You just have to make sure to clear out containers as you traipse along

There are several options available to help solve your ammo problems, the first is to start making your rounds to the merchants that sell ammo (caravan and scavengers included), turn down your difficulty level (higher difficulty make enemies bullet sponges), get the perk scrounger (the one that adds more ammo in containers), open every single box, ammo crate, footlocker, locker you find, also loot every corpse you find, and lastly, learn how to be more accurate with your shooing (instead of spray and pray, try sniping where possible, and get that critical hit)

Oh yeah, and if you don't mind exploiting glitches, then use the Gary glitch (Operation Anchorage) for nearly unlimited ammo.

Follow some or all of these steps, and pretty soon you will find yourself selling your ammo cause you've got too much of it.

I'm having this very same problem... level 15, no .556, no .32 and 20 rounds of 10 mill. But I look forward to replenishing my supply after some scavving. Rivet City, has two vendors who sell ammo, TenPenny has two as well. Also, check in with Harith, after you invest in him he has a crapload of ammo.

I killed a bunch of supermutants at some church and i was rewarded with ~20 rounds of .32

Having to treasure every round does add some fun, but only if there's ammo available for me to treasure

Gun down and loot raiders and/or mercs, or visit Flak & Shrapnel's.

That's how I usually amass my ammo cache.

Pro-tip: When you kill an enemy, pick up the weapon they drop before looting the body. You'll gain a few extra rounds of ammo that way.

I've found with my gunners that unless I know I have a surplus of ammo I stay away from any automatic fire weapons. Single bullet projection is far more ammo efficient in and out of V.A.T.S.
Use a 10mm pistol instead of the SMG. Carry a combat shotgun so you can use shells, a magnum for the .44 ammo you find, your hunting rifle for the .38, and a sniper rifle for the .308 (There's one in a cache just outside Megaton)

If you never sell the ammo you find this should keep you shooting. If you trade the other junk you find for more ammo with merchants, caravans, and scavengers you should be sitting pretty.

There's a nice stash of ammo and chems at the Super-Duper Mart when you do Moira's Survival Guide quest.

Also try standing outside Megaton and waiting for two hours at a time until all merchants have passed through.

Your Luck SPECIAL will come in handy here. If it's high enough you will get more critical hits, resulting in less ammo used, and you will find more ammo in containers too.

Good hunting!:)

Another idea is to pay a visit to Fort Independence, located just west of Fairfax Ruins, and talk to Protector Casdin there. He offers you a job scavenging for technology and trades you (among other items such as frag grenades and stimpaks) 5.56 mm ammo for items such as scrap metal, laser pistols and rifles, and such. Don't worry about their condition - he'll take them even if they're broken, and gives you the same amount of ammo as he would for items in 100% condition.

Even if you don't have weapons that use 5.56 yet, you can always trade it for ammo you can use.