“Six-shooter coffee” was a popular drink at the president’s LBJ Ranch in the 1960s, but the term is seldom used today.
 
 
Legends of America slang page
Six-shooter Coffee—Strong coffee
     
Museum of Education cowboy vocabulary
Six-shooter coffee—good, strong coffee
     
29 January 1954, Dallas Morning News, “Frontier Cowboys Strong for Coffee,” part III, pg. 2:
The cook put plenty of Arbuckle’s in the pot and boiled it for half an hour. Some called it six-shooter coffee. It was so strong, they said, that it would float a pistol.

15 August 1964, Eureka (CA) Humboldt Standard, pg. 5:
There will be barbecued beef with hickory sauce, barbecued ribs, barbecued chicken, German potato salad, Texas cole slaw, ranch beans, sourdough biscuits, fried apple pies, Spanish olives, dill pickles and “six-shooter coffee.”
 
“That’s coffee that will float a .44,” said Walter Jetton, Fort Worth, Tex., a catering firm head who has been staging barbecues at the LBJ Ranch the last 10 years.
 
13 November 1964, New York Times, pg. 1:
JOHNSON CITY, Tex., Nov. 12—President Johnson welcomed the President-elect of Mexico today, put a five-gallon hat on his head and took him to a barbeque on the banks of the muddy Pedernales River.
(...) (Pg. 15—ed.)
At 1 P.M. the party bumped along a road from the ranch house to a grove of live oak trees near the river to eat a lunch that included barbecued beef and ribs, chicken, hot link sausage, German potato salad, beans and “six shooter coffee.”
   
6 May 1965, Chicago Daily Defender, “The Fast Gourmet” by Poppy Cannon, pg. 22:
SIX SHOOTER COFFEE ... It’s strong. It’s hot, it’s…lots.
   
4 July 1965, Los Angeles Times, pg. G33:
For non-calorie counters, there’s the LBJ BARBECUE COOKBOOK by Walter Jetton (Pocket Books: $1). The author, the President’s personal caterer, imparts the ingredients for his barbecue sauce, as well as how to prepare a real Texas repast over the coals. There are numerous recipes for such dishes as Settler’s Stew, Chuck Wagon Hash, Corn Flapjacks and Cowboy Potatoes. If you wonder what kind of coffee they serve at these outdoor Presidential soirees, this is Jetton’s formula, one which he calls Six Shooter Coffee:
 
“This will float a Colt .44 and is the best coffee you can make…Put a pound and a half of ground coffee into a pot with a gallon of water and boil the hell out of it. Do not worry about boiling it too long for there is no such thing. Set it aside for a few minutes for the grounds to hit bottom before you pour it.”
   
20 October 1966, Long Beach (CA) Independent, pg. 13Z:
The term “six-shooter coffee” was coined by cowboys, who claimed their morning brew was strong enough to float a .44 bullet.