After reading your question, my guess is that you are supposed to write a one-paragraph essay answer about the short story "The Gun Without a Bang." (In a five-paragraph essay, the important statement is the "thesis statement" and the "topic sentences" sometimes called "focus sentences" are the first sentences of each paragraph that reconnect to the thesis.)
I would suggest the following focus sentence for your one-paragraph essay that will contain three supports:
Considering Dixon's pride, there is great irony in Dixon's switch of weapons from the beginning to the end of the story.
Your paragraph should begin with this focus sentence and then give three supports.
I would begin your supports with showing Dixon's pride. He is confident with his gun and feels as though nothing can hurt him while he has it in his hand. His short and muscular stature (and his finely curled mustache) nicely show his pride. Most of all, though, his pride is shown through his bragging about killing many alien species through a vast array of space-age weapons.
Your second support should be about Dixon's insistence on using the disintegrator gun. His reasoning of the guns importance boils down to the American past and how the "West" was won. Dixon answers simply: "the bow and arrow vs. the Colt 44." This shows his preference of a gun over a "primitive" weapon such as the bow and arrow used by the Native Americans.
Your final support should be about Dixon switching BACK from the disintegrator (which he now simply uses as a hammer) to the bow and arrows that he makes himself in order to survive on the planet. In fact, it is the disintegrator gun that causes such damage to his space ship, that Dixon cannot return home and is presumed dead. As a result, he has to live on the planet with the scary creatures. Because the gun made no sound, the animals were never afraid of it. It took the piercing pain and blood of the bow and arrows, with the animals walking around horribly wounded before they died, for them to learn to avoid Dixon. Dixon runs full circle by switching back to these primitive weapons. He survives and is rescued as a result.
A good quotation to use might be as follows:
Making the ultimate anything takes the ultimate thought -- and how ultimate is ultimate?
This, of course, is in reference to the "ultimate" weapon, ... is it the disintegrator? ... or is it the bow and arrow?