How do you equip weapons to your companion and have them keep them equiped?

I gave Nick a flamer and he used it for alittle while then equiped his pistol again. The only success i had was giving piper kellogge's pistol, she kept it equiped until i took it. Is it only certain weapons they can have?

Trade the items with them, then while in trade window (if on PC) press T while pointing at item (that's now in their bag) you want them to equip.

You need to give them ammo for the weapon you give them as well. If they run out of ammo for that weapon they'll switch back to their default weapon.

Piper with a super sledge and power armor is scary.

Sounds like he ran out of ammo. Give them ammo too!

I'm pretty sure you can just give them 1 unit of ammo and they won't need anymore. Can't confirm for everyone but has worked for my sanctuary settlement so far on.

Doesn't work that way for companions, they use up all ammo and switch to the next best weapon they have ammo for available, if there are none they'll use the default weapon