Looking at your writing, I'd say the particular description of the firearm is the least of your worries. In your particular situation and what appears to be your level of writing you may want to consider subscribing to the philosophy that less is more. The less words you write, the better the chance you'll not have a fundamental failure in the writing. You may wish to just refer to the gun by a generic description as this will have the least amount of detail which will or may be written poorly and/or inaccurately. Phrases such as "handgun," "semi-auto," "revolver," "black," "steel," and so on will convey the information just as successfully as "North American Arms, Inc. Black Widow with fixed sights and a Magnum Grip Holster loaded with 35 grain rounds."
And an aside, raise your hand if you went to college at a time when you had to know grammar and spelling and you would have been failed for ever writing like that.