All settlers come default with a calibre .38 gun and a few rounds for it. What I am curious about is if say I give a settler a calibre .308 gun and tell him/her to use it, do I also have to provide the ammunition for said gun or, does the settle have infinite ammunition for what ever gun they are using? I wonder cause the young fellow at Finch farm picked up a flamer and seems not to have problems using it. Now I don't know how much fuel was in the flamer when he picked it up and he used it without me telling him to do so.

I could naturally give all my settlers in a settlement a higher calibre gun, take away their default gun and then wait and see what happens. Unfortunately I'm a bit lazy and don't want to #1: wait for an attack to happen. #2: Run around finding and then use valuable resources repairing any damage that might have happened.

So, anyone know about this?

Yes, you need to provide the proper ammo for the gun. I'm not positive how many rounds you need to give however. I just give enough for one load of the gun, e.g. 30 5.56mm for an assault rifle.

Thanks rstuck

All you need to give the settlers is one round for the type of weapon they have. Somehow they miraculously use the same round over and over again. I normally give them 10 rounds for they type of weapon and call it good. Slightly off-topic but relevant, it is funny when a settlement gets attacked and every settler pulls out a minigun and rips the attackers a new one.