Blanks and Blood

I come to zero conclusions in this post.
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For some reason, fake muzzle blasts look... not as awesome as they should. So I'd like to know why. I'll start by the notion of the "performance" with a weapon.
I only watched all of Heat for the first time a few weeks ago. How many times did you re-read the previous sentence to figure out what it meant? OK, it means I just watched the movie Heat.
Anyway, they have a lot of M-16s and variants in that picture.
Then I was looking at clips of Die Hard online. Lots of MP-5's in that picture. Those are the short-ish machineguns that John McClane has.
So here's the thing. Those movies use a lot of blank ammo. The M16's use NATO rounds and the MP5's are 9mm (usually). And for an automatic weapon to shoot blank ammo those blanks basically have to have the same amount of charge in them as real bullets. (The guns themselves are typically modified so they can't accept live ammo but otherwise they cycle just like fully working guns, from which they were made.)
Actors. Firing automatic weapons.

The guns do not kick much. I mean compared to a handgun (which has a LOT of kick), the barrels on those weapons stay fairly in place.
So if you're using a modern machinegun or assault weapon, and putting the flashes in later, you perhaps don't need to shake the gun when shooting. The gun might crawl up the target as the weapon pulls (my dad told me that was a problem with the "grease guns" he trained with in WWII) but the designers and manufacturers of modern weapons go to a lot of trouble to minimize the amount that the gun jumps around when shooting it.
Again this is not the case with handguns, which is why the 22nd Century version of me complains about 21st Century handguns all the time. Plasma weapons do not jump.
So where was I? Oh, it's like that Chekhov thing where drunk people do not act drunk. When you shoot you don't necessarily let the gun recoil the way you might think it should recoil. If you're pretending. To shoot I mean.
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But the question for me is why does the flash look so crappy when you add them in post?

• The images used are 2D and suck for that reason.
• The flash doesn't light up the area the way flashes from a gun barrel should and suck for that reason.

There's all kinds of fancy tools for making the flash be unique and pseudo 3D can make the flash look like its coming from the right direction.

So I don't know. Maybe it's the lack of light on the face of the shooter? We've experimented with using a strobe light. Dumb rolling shutter on the camera makes for frames that are half lit up and half dark. So we don't know if that experiment would have really worked.

I'm a fan of 2D blood. I know. You aren't. But I am. But that's for another post.