For this, you will need a script, that I DID NOT Make!

First, go into C:\Program Files (x86)\Steam\steamapps\common\Half-Life 2\hl2\cfg
Copy one of the cfg files.
Next, rename it to whatever you prefer. I've simply named mine pistol.
Now, copy this text into the cfg file.

Bind "MOUSE2" "+1"
alias "+1" "alias 3 +2; +2"
alias "+2" "+attack; wait 2; -2"
alias "-2" "-attack; wait 3; 3"
alias "3" "+2"
alias "-1" "alias 3 -attack"

Now, save that.
Go into your game, open your console, type in "bind t "exec pistol"
And this will enable the pistol script. (Hold down right mouse to shoot as fast as possible)

Now, we will learn how to zoom and shoot at the same time, useful for the AR2 And 357.

First, go into your hl2 cfg folder again. Copy the pistol fire script.
Rename it to whatever you prefer, just like last time.
Next, delete everything in the text file.
Then, copy this script into it:

alias +zoomer "toggle_zoom; sensitivity 8.5; exec 2.cfg"
alias -zoomer "toggle_zoom; sensitivity 11; exec 3.cfg"
bind MOUSE2 +zoomer

alias +spread "+attack; exec 4.cfg"
alias -spread "-attack; exec 5.cfg"
bind MOUSE1 +spread

alias +attacker "+attack"
alias -attacker "-attack"
bind MOUSE1 +attacker


Ok, you're done with this part, now for these 2 to be compatible with your controls.

Now, go in your hl2 cfg folder again. Copy a cfg text file.
Rename this:

autoexec

Now, put this into it:

bind t "exec (Whatever your pistol cfg text file is named)"
bind y "exec (Whatever your zoom script cfg file is named)"

Side Note: You may want to bind your alt attack to MOUSE3 Since MOUSE2 Is already being used.