The best way to learn proper English is to read news report, and watch news on TV. Watching TV shows is a great way to learn casual English, slang words, understand culture reference and humor. If you have already watched these shows then you may recall the words used in the following dialogs.

This RIFLE is for big-game hunting,
not for birds.
Money Heist Season 3, Episode 8

Sit down. Now calm down, the three of you,
otherwise, a blow with the RIFLE.
Money Heist Season 1, Episode 1

and fired on me with
what I ascertained to be
an M16 assault RIFLE.
Breaking Bad Season 2, Episode 3

...a marshmallow-shooting RIFLE...
The Big Bang Theory Season 4, Episode 4

I could grab my RIFLE, crack your skull,
leave you fucked...
Money Heist Season 3, Episode 5