How Does it Work: Blowback Action

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Shared January 10, 2019

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How Does it Work: Blowback Action

The simplest for of firearms action is blowback, also called simple blowback. It is basically just an application of Newton's 3rd Law; that for every action there is an equal and opposite reaction. As the bullet moves forward down the barrel, the slide or bolt of the gun moves backwards. The two move with the same energy, meaning that the light and very fast bullet is balanced out by the heavy and slow bolt or slide.

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Jason Goodman

Hi, physics professor here. Great video, with one important mistake: recoil depends on conservation of *momentum*, not energy. Your explanation is perfect, you're just using the wrong word in this situation. Momentum is simple to understand: it's literally mass times velocity. So if the slide weighs, say, 50 times as much as the bullet, it will move 50 times slower. And so in the time it takes the bullet to go 100 mm down the barrel, the cartridge goes back 2 mm. Kinetic energy is also a combination of mass and velocity, but a different one, and it's not equal between gun and bullet. The bullet gets a lot more energy than the gun, unless they weigh the same.

6 days ago | 381

Rock Island Auction Company

Love this series! Keep 'em coming.

6 days ago | 218

based! Burgundian

And here I thought a blowback was a refund from a prostitute.

6 days ago | 455

Shiladitya Talukder

Cool! Are you bringing more videos of this type?

6 days ago | 355

Spoiled Moronic Man-child

- How does it, em... how does it work? - I know not, my liege. - CONSULT THE BOOK OF ARMAMENTS!! - Armaments, chapter 2, verses 9 to 21: - And saint Karl raised the gun up on high saying: "Oh Gun Jesus! Bless this Thy blowback-gun, that with it thou mayst blow thy enemies to tiny bits, in thy mercy!!"

6 days ago | 136

Erik Jonsson

After being mocked for my lack of gun knowledge (zero gun home) I tried to learn the basics on my own. A video like this would have been a godsend instead of watching old 40s wartime instructional videos. Much appreciated Ian and keep it up!

6 days ago | 183


Momentum is balanced, not energy. The bullet has far more energy than the gun. Their momentum is equal.

6 days ago | 92


Newton's third law isn't about balancing the energy (J) but the force (N)! The force applied to the bullet and slide are equal and so the momentum (m x v) of the bullet and the pistol are equal. The slide and bullet don't end up with equal kinetic energy (0.5mv^2) because the bullet is much faster.

6 days ago | 76

Jay Massengill

Archduke Ferdinand just clicked the dislike button...

6 days ago | 18

00 Josh

I was wondering why it was so hard to find a blowback-operated rifle chambered in 300 Winchester magnum...

6 days ago | 13

Sean Crooker

Why didn't you use a example from your Hi-point collection? Please don't block me

6 days ago | 12

Adolf Hitler

Last time I was this early i was still in prison

6 days ago | 31


last time I was this early the chinese were still trying to ingest gunpowder for eternal life

6 days ago | 24

Brian Steehler

Ian, I’m so glad you are doing these videos. My friend said to me yesterday that he likes your videos but wished he knew more about the terms and systems of firearm operation. You have a great teaching style, a good method of demonstrating the material, and excellent editing of firearms in operation. Please keep it up.

6 days ago | 8

nick highland

Browningbrowningbrowning makes the best blowbacks

6 days ago | 26

Joachim Elmesiöö

Seeing how much mass is usually put in to .45 or 9mm submachine gun bolts, is there a proportion to how much energy is in less powerful blowback handguns, or do they handle it in a different way? If the SMG bolts are proportionally heavier does it have an advantage?

6 days ago | 17


As far as I remember, momentum is conserved, not strictly energy (because there are instances that momentum is conserved but energy is not)

6 days ago | 11


What is that gun at 2:55? It has an interesting mechanism, as if the bolt were on the outside, not inside.

6 days ago | 3


Already know how it works, still always love your content no matter what you upload :D

6 days ago | 13

Andrew Burke

I like this new format for these sorts of subjects Ian. And it looks like many others thing this - at this point, 431 likes, no dislikes!

6 days ago | 6