calculating recoil/kick

[akodo]

Okay, we all know that kick is subjective, with factors like shooter tolerance and stock fit playing a big part.

But there are parts that can be predicted and measured, such as actual recoil forces.

So here's my question. I googled a rifle recoil calculator up, and it asked for grains of powder.

Humm...why? (also, how would you know for sure how many grains are in a factory case)

So after putting in fixed values of bullet weight, bullet velocity, and rifle velocity, I played around with different powder weights, and the recoil value changed.

Why does it matter how much the powder weighs? What does that change?

After all, not all powders are the same. It may take 55 grains of powder X to have a 130 grain 270 bullet reach 3150 fps, but 60 grains of powder Y to reach that same velocity.

I'd think the recoil from both would be the same, as long as the rifle weight, bullet weight, and bullet velocity are constant.

Why does the WEIGHT of the grains of gunpowder matter? (after all, some powders are more potent than others)

 

[Oro]

Why does it matter how much the powder weighs? What does that change?

Because mass is not created or destroyed, so the weight of powder goes somewhere - and it's expelled as both gas and particulate projectiles. Look at a slow-mo of a gun being fired - you can see gasses leaving and unburnt powder, too. Since it's mass that's in the gun and then leaves, it does factor into recoil.

For all intents and purposes, the recoil is the same as the powder weight is relatively inconsequential. Try running the calculator disregarding the powder and you'll see the overall results changes very little in real terms. Keep in mind the calculator is trying to be as accurate as possible, so it includes it.

 

[Jim K]

The powder weight is relatively inconsequential in some handguns, but in a rifle firing a 150 grain bullet ahead of 50 grains of powder, the powder weight is 1/3 the weight of the bullet and is 1/4 of the total moving mass. So it is certainly not inconsequential.

If burning propellant and oxidizer were not part of recoil, those huge rockets would never get off the ground. We seldom think of it that way, but men went to the moon on recoil.

Jim

 

[rcmodel]

(also, how would you know for sure how many grains are in a factory case)

1. Pull the bullet and weigh the powder.

Or:
2. Look at any reloading data for the caliber and take an average weight of powder used with that bullet weight. While not exact, it will be close enough for GooberMint work.
http://data.hodgdon.com/main_menu.asp

rc