Notes on Weapon Selection
If you have the option, you want to pick the weapon that supports you and your character. You also want to keep in mind how the weapon functions may influence how a scene plays out. 

Hypothetical Situation:
You have determined through research that the police agency, to which your character belongs, uses the Glock 17 as it's issue firearm.

Let's say that your character is a cop on the edge and is in the middle of a big standoff with his/her nemesis. You want them to cock the gun for dramatic effect. But you can't, the Glock is a "hammer less" gun and can't support the scene as you visualize it.

Here the author must choose between authenticity of the and poetic license. Apart from the past and present members of that police agency, who will know what weapon they are issued? Can a weapon, that is in general use by law enforcement, that meets the plot requirements be substituted? If so, what pistol will be the proper fit?

If you have complete freedom to choose what the weapon of choice will be, I suggest a place holder for your draft (xxgunxx) that is easily searchable. After your story has followed its' organic processes, you can then pick the weapon that fits and paste in the full nomenclature or the "weapon pronoun."

Notes on Weapon Detail
When do you need to get down in the weeds when describing the weapons you are using in your story?

1. When some attribute of the weapon directly influences the plot:
How many bullets does it hold
How it's reloaded
What type of safety does it have

2. When you want to use the way the gun operates for dramatic effect:
{He pulled back the hammer, "You're gonna die now, scumbag!"}

3. When the type/make/model of weapon needs to reflect what an organization actually uses:
{The Cop drew his Beretta.}

4. When the action scene requires detail (Elements of plot / Dramatic effect part 2)

The cop drew his Beretta 92f, flicked off the safety, and covered the crowd. If backup didn't get here soon he was in big trouble. With only 15 rounds in the magazine, he was going to run out of bullets before he ran out of targets. And things were going down hill fast.

You don't need the same level of detail if the description is going to get in the way of the moment:

{The mugger stepped out of the shadows and pointed a gun at him. Crap, it was the biggest thing he'd ever seen!}

The level of detail you use should ultimately support the scene or your character's knowledge and experience. Once you've established that your character carries a Beretta 92f, you really only have to refer to it as "The Beretta," 92f is understood. Think of this as weapon pronouns. Like a pronoun, sometimes the full nomenclature must be used. This will be dependent on the context.

Notes on Jargon & Lingo
It's important to take your audience into account when explaining the technical aspects of the weapons you are using, but you must also apply this line of thought to your characters and the way they refer to weapons and their components.

The thing to remember is context. If the paragraph/passage is describing the way your experience/trained character views a situation, then lingo and jargon is good.

If the character is untrained, then common misuses of terminology, poor weapon knowledge and handling are to be expected.

If the passage is descriptive of the actions of characters or equipment, then you should go with technical nomenclature, or possibly, a combination of nomenclature and jargon that makes sense as the action shifts around your characters. In this case context drives all.