how animation Uperbody alone or better animation transition ?

Hi i have a animation on my character, walk with a rifle, this is a tatical walking like SWAT, but a have the same walk animation buts is walking and shoting, to merge this two animation, whe i shoting the legs dont look realistic, because i can shoot any time, and animation transition dont look good, how i do to animation uperbody…hands, arms…and the legs dont transition ?

Take a look at this tutorial series:

thanks fighter5347 i did just follow this video - YouTube