Murray Comics published plenty of digest-sized romance comics, and a few odd horror issues too, but Shootout is the only western digest-sized issue I've seen from them.
See the sample pages below for the contents. It appears to be Charlton material.
I doubt this is the only digest-sized western from Murray. As Taylor said in Planet of the Apes, "Where there's one, there's another."
And I wonder whether there is a dedicated imprint - Murray Western Library - ala the Murray Romance Library.