Disclaimer up front. In films, guns can be awesome. In the real world, they can be terrifying and dangerous. As such, when working with firearms in films, safety is always your first concern. There is no reason to take risks for something that can be done quite simply and without ever introducing real firearms to your production.
Sound good? Great. Now, let’s lock and load and dive into everything you’ll need to create realistic (and SAFE) gun effects in your films and videos.
Realistic prop guns
To start, you're going to need your stock your armory with plenty of weapons. In this tutorial by Film Riot, the guys show how they were able to turn some cheap toy guns into realistic looking props. You can find some affordable options at your local Walmart, or you can always find some online on Amazon or eBay. In the video, the guys also show you how they were able to spray paint the orange caps black and add some gray tinting to make them look more realistic.
Once you have your guns in your scene, you can add everything else in post. Your first step is usually to add a muzzle flash to give your gun that explosive look. The tutorial below might be a little bit old, but it shows how simple the process can be. All you have to do is find a muzzle flash online (plenty of free options and packs available) and layer it on in After Effects (you can do the same in Premiere Pro, too—more on that below). The trick is lining up the flash to the right point, over the right duration of frames and with the right blend.
Smoke and lighting effects
In this tutorial by RampantMedia, we get to go a little more in-depth on how to work with the flashes, and more specifically, with the smoke effects. The video explains how to add lighting masks in your edit in Premiere Pro to give your gun shots a bright pop on your characters and the surrounding environment for that extra dose of realism. The tutorial also links to a huge free collection of action effects for you to download and try out on your own.
Now this is really cool. If you really want to sell gun battles in your films, you need to sell the impact and damage. To put it more bluntly: a gunshot is cool, a zombie head exploding is awesome. This two-part tutorial shows you how to make movie-quality squibs for less than $25 without using any dangerous pyrotechnics. As long as you don't mind some sticky corn syrup getting on your character's costumes, this is your best way to go.
Finally, to really sell your gun effects, you need your guns to sound real and lifelike. While you can always record some yourself (which can be quite tricky for logistics and audio capture reasons), you may be much better served finding gun sound effects online. Many of the free muzzle flash and VFX packs include gun sound effects, but if you want a complete arsenal, a full gun pack like the one offered below may be your best bet. However, always be prepared to tinker with the sounds in post a bit to make sure they accurately reflect the setting in which they are fired in your film.
If you need more gun resources, here are several more packs and effects for you to comb through to find the right ones for your project.