Meanwhile, we took his gun apart to see if there was anything wrong. Mechanically, the gun was fine, but it was awash in oil. Grit, dust, and powder residue stick to oil and gum up the insides, and that can be enough to make a gun stop shooting, even in 80-degree weather. When it's cold, it's even worse, as some oils will thicken. Often, brand new guns will misfire a time or two because there is still grease on the firing pin.