what is the size of your weapon?
i do this method to simplify my weapon sprite creation:
i make all my weapon sprites 320x180 and place the weapon in that sprite as i want it to appear on the screen
this makes it fit exactly as i want it to at scale 1, and i dont really need to fiddle with the position. setting the y position to about 30 to 50 compensates for the weapon bobbing. it also makes it easier to align my weapon animation frames cuz the images i am making represent exactly what is on the screen.
if your weapon sprites are huge, then at scale 1 they are just too big for you to see them without adjusting the scale to 0.1 or some such. just play with the scale if you are adamant about having large sprites for the weapons.