Block change scale when insert into another drawing

i have created a block with attributes in full scale (1'=1'-0") and when i tried inserting it into my 1/2"=1'-0" drawing the block keeps on rescaling itself. 

my block is a circle with a diameter of 5/16" in full scale and when i insert it into my 1/2" scale drawing the block appears to be extremely small and why i measure it, it is the right size. why is that and how can i fix it? so the block wil appear in full sacel size in my 1/2" drawing.

here are the steps i took to create the block:

1. open a new drawing 

2. MVSETUP to full scale

3. draw circle with diameter of 5/16

4. i added my attributes

5. used block command to create a block.

i don't want to have to be constantly redrawing the circle and manually typing out my text in the circle. 

thanks.