Resizing a MC according to the loaded asset (jpg, swf...)

Hi,

I have tried many things but when i load my external jpg inside a MC (thru the use of a MovieCliploader which then load the jpg inside that MC in an empty MC).
I have put my code in the onLoadInit() and did something like

MC._width = target._width;

My MC has a specified width and height in the library. is it because of that or should i put it smaller.

target._width = MC._width;??