There is no WSM for the AR15.
There is however, the WSSM calibers in 223, 243 6.5 and 25 all in WSSM calibers, "Winchester Super Short Magnum".
The WSM "Winchester Short Mag" will only work on an AR10 platform.
There is considerable amount of case legth difference between the two. If you have any questions regarding the two, I suggest you contact Dtech, Mike will be more than willing to walk you thru the needs and differences of the two calibers.