Joe;
As I recall I read this in a book on building reproduction long rifles back in the late 1960's or early 70's. I was building one at the time & took it to heart & slotted my barrel lugs.

I posted this because the above linked article implied that Longitudinal shrinkage was not a problem. Wood can, & Does, shrink longitudinally as well as radially & Tangentially,

Miller/TN
I Didn't Say Everything I Said, Yogi Berra