A lot of Old Jack's books are actually collections of articles and the flow suffers a bit I think. Still well worth reading, of course.
Didn't see it mentioned, but Stephen Hunter's "Pale Horse Coming" features thinly disguised versions of Jack, Elmer, Askins, and Ed McGivern assembled into a team by Earl Swagger to break the inmates out of a slave-labor prison camp in the deep South. It's a decent read for gun cranks and the Askins clone comes across pretty much like people seem to think he was. I'm surprised no one has made a movie out of it.
