Felt recoil: 124 gr vs 115 gr

I practice with Federal 115 gr FMJ 9mm ammo from Walmart, mainly because it's the lowest cost, readily available ammo I can find locally (at $10.47 per 50-round carton), it burns reasonably clean and I've not had a single malfunction with over 2,000 rounds fired.

I run Federal's 124 gr JHPs for carry, and I fire them now & then at the range.

Unexpected observation: the 124 gr JHPs shoot SOFTER than the 115 gr FMJs.

I know little about ballistics, but I would think that the higher the grain count for any given caliber, the greater the felt recoil. How it can be that 124 gr rounds produce less felt recoil than 115 gr rounds?

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Originally Posted by ubervic

I know little about ballistics, but I would think that the higher the grain count for any given caliber, the greater the felt recoil. How it can be that 124 gr rounds produce less felt recoil than 115 gr rounds?

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http://en.wikipedia.org/wiki/Recoil#...tion_of_recoil

JV-
Thanks for the link to the information.

I guess I'm slow, though, because I'm still unclear as to how a 124gr round can shoot softer than a 115gr round through the same pistol. Is the point that the hollow-points are significantly lighter than the ball ammo?

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Originally Posted by ubervic

JV-
Thanks for the link to the information.

I guess I'm slow, though, because I'm still unclear as to how a 124gr round can shoot softer than a 115gr round through the same pistol. Is the point that the hollow-points are significantly lighter than the ball ammo?

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The heavier round takes longer to accelerate so the recoil is perceived as less harsh because it's more spread out.

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Originally Posted by commandar

The heavier round takes longer to accelerate so the recoil is perceived as less harsh because it's more spread out.

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All else being equal.

As a general rule, for any given power factor (bullet momentum, measured as velocity in fps times weight in grains divided by 1,000) the heaviest bullet will have the least felt recoil.

But if you were to compare, say, a full power 10mm 200gr Norma load to a .40 165gr Hydra-Shok (which is a reduced recoil load), the heavier bullet has substantially more recoil.

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Originally Posted by commandar

The heavier round takes longer to accelerate so the recoil is perceived as less harsh because it's more spread out.

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My understanding is this.

First, understand that "felt recoil" == the amount of sudden movement. More movement, more suddenly, yields more felt recoil. Also understand, intuitively enough, that more energy == more sudden movement, for a given bullet weight. From there, it's easy to see that a lighter projectile == more sudden movement, for a given amount of energy (e.g., a normal 9mm load.) You can think of the movement of the gun as "being caused by" the movement of the projectile. When a lighter projectile moves more suddenly, so will the gun - giving more felt recoil. A heavier bullet will be moved less suddenly by the same amount of energy; therefore, the gun will move less suddenly; therefore, the felt recoil will be less.

Make sense?

To Todd's point, a 10mm load has a lot more energy than a 9mm load, so the felt recoil is more, even though the bullet is heavier. I guarantee you, though, that if you could load a 10,000gr projectile into a 10mm case, the felt recoil would be minimal. Who knows, such a load might even be a best seller. ;)

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Originally Posted by mariodsantana

I guarantee you, though, that if you could load a 10,000gr projectile into a 10mm case

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http://blog.amhill.net/wp-content/up...e-accepted.png

a 1.4 LB projectile would be interesting to see.

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Originally Posted by JV

a 1.4 LB projectile would be interesting to see.

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Throw this:
http://ecx.images-amazon.com/images/I/31SDCXNZ0TL.jpg

Glad I could help. :cool:

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Originally Posted by ToddG

Throw this:
http://ecx.images-amazon.com/images/I/31SDCXNZ0TL.jpg

Glad I could help. :cool:

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Oooooh, bonded!

9 mm has recoil??? No one told me that started adding recoil to 9 mm--when did this start happening???

I've fired some Hirtenbirger 9mm 124 that was pretty stout, years ago, from a Glock 17. L7A1, IIRC.

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Originally Posted by DocGKR

9 mm has recoil??? No one told me that started adding recoil to 9 mm--when did this start happening???

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Ha!!! ;)