This monthly, cheap, small, 'pulp' magazine carried one main story a month, along with other material.
Issue number one appeared in April 1948. The last issue, number 159, in August 1961.
Phil Stephensen-Payne's incredible
site Galactic Central has
a page which currently displays about 50 of the issues, on which can be seen the four noted below
by way of this link.
The main story in each issue of the magazine is featured on the cover, accompanied by a suitable illustration, not from the book's original artwork.
From the illustrated copies Mike found that between 1951 and 1953 the magazine carried four Hank McCoy stories as their main feature.
Killers of Red Canyon in Issue No 42, dated October 1951
Sonora Trail in Issue No 45, dated January 1952
Wild Horse Range in Issue No 55, dated December 1952
and The Hides of Texas in Issue No 59, dated April 1953
As only a third of the magazines are shown, it seemed quite likely that more than the four Hank McCoy westerns were featured in this magazine.
Further hunting has led to Mike's conjecture being upheld. He found, on the University of Melbourne's site, further evidence.
On the site is a pdf file titled taylorcollectionlist.pdf .
This list - again incomplete - of their collection of Western Monthly issues added the following four titles:
Three by Hank McCoy:
Guns Across the Sholto in issue No 43, dated November 1951
Marshall of Savage City in issue No 63, dated August 1953 (note the change to the title)
Blood on the Pecos in issue No 67, dated December 1953
and one as by Brett Cameron:
Blue Sombrero in issue No 64, dated September 1953
And so it seems that all but one of the Hank McCoy stories and at least one other were published
in Western Monthly. A total of eight books known and with the definite possibility that there may
have been been others, not yet discovered.