SteyrAUG's "Shrike" thread got me to wondering. Any patent protection that the "Shrike" might have is about to run out -- U.S. patent 4,942,802 expires on September 24, 2007 (assuming they paid the fees for the full twenty years of protection). Glock's original design protections expired several years ago ("coincidentally" right around when they suddenly started producing the integral rail mount, which they also patented IIRC). Calico's protection on their helical magazines is about to run out, too.
Olympic Arms got a patent on their OA93, although IMHO it is so weak that anyone could work around it without much difficulty (doctrine of equivalence or no).
What other mechanisms and considerations are there in the gun industry to prevent, e.g., S&W from duplicating, e.g., the Glock (like that would ever happen!
)? Or is it a free-for-all, with anyone allowed to duplicate any design once the patents run out?