It's hard to tell much because of the CGI effects but you can see the amount of recoil.

So when you see a person gunning full automatic guns and manages to stand still and not moving back at all, you'll know that person was firing blanks.

Nowadays, actors try to make it look like it recoils by moving their shoulders back a bit and shake it when firing full-auto, if you have watched Rambo movie you will understand with his sophisticated weapons.

Another best way to recognize blank bullet is to look for crimps around the mouth of the case. Normal ammunition has a projectile seated in the neck of the case, whereas blanks will not have a projectile (although some very old .303 Enfield blanks did use light, wood bullets) and the neck will be crimped, instead. Some nations paint the tips of their blanks with blue paint so as to ease identification

To understand how blanks work, first we must clarify the difference between a bullet and a cartridge, two terms that are often confused.

A bullet is the piece of a cartridge that flies forward in order to strike a target.

The gray lump that's labeled 1 is the bullet. Typically, these contain a lead core that's enveloped in a harder metallic case. Bullets poke out from the top of a shell (2), which also houses gunpowder (3) or a similar substance.

Now, look at the shell's bottom. Down there, you'll find both a rim (4) and a primer (5). When the gun's trigger is pulled, a firing pin strikes the primer, causing the powder to ignite. As it burns, it rapidly releases gasses that build up with enough force to launch the bullet out of the cartridge and through the gun barrel.

In contrast, blank cartridges work by doing away with metal bullets altogether. Instead, the top of the shell is crimped or covered with a wad of paper, plastic, felt, or cotton. (The wadding or crimping prevents gunpowder from spilling out.) Fire a blank, and you'll still get that convincing gunshot noise. Because there is no bullet to be propelled as a result of the explosion, these special cartridges aren't likely to injure anyone-unless, of course, they're used improperly.

Make no mistake: blanks can kill. In 1984, actor Jon Erik-Hexum died while on the set of CBS's Cover-Up as a result of a blank cartridge. Bored by incessant delays, the actor pointed a gun loaded with blanks to his head and reportedly said, "Can you believe this crap?" before pulling the trigger.

He had pressed the barrel directly to his temple, and the force of the explosion still did incredible damage, even without a bullet. It drove a small chunk of his own skull into his brain, which caused severe hemorrhaging and put him in a coma. He died as a result of his injuries.

"Blanks aren't toys," warns firearms dealer Bob Lesmeister. "You have to remember that the force of the exploding gas is great enough to fire a bullet." In fact, some blank cartridges contain more gunpowder than regular ones in order to ensure an extra-loud sound.

Jon Erik-Hexum's death wasn't an isolated incident. Blank cartridges have been responsible for multiple reported fatalities. As with all forms of ammunition, caution must be exercised when dealing with these rounds