Know a machinist? An end mill will male short work of that weld.
If not, dremel or grinder with a cut off wheel. You will likely need to gouge into the hider some to get all of the weld if the pin is not a tight fit to the hole.
Clamp the barrel with the pin job at 6 o'clock position, work the hider back/forth gently while tapping the opposite side of the hider with a dead blow mallet or similar. The pin should drop out.