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Old 02-01-2010, 18:55   #1
oISHUTupNrocKIo
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Grains, FPS, Energy...?

Sorry if this was asked before guys, but I'm so confused. I seen cartridges with less grains have more FPS and higher engery. i.e. a 180 Gr 10mm Buffalo Bore has around 782 LBS/FT and 1350 FPS, but a 200 Gr cartridge has 639 LBS/FT and 1200 FPS... if someone dosn't mind, can you explain what grains and all this technical stuff means? I've been shooting for 6 years and never really paid attention and would like to reload one day. Thanks...
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Old 02-01-2010, 19:07   #2
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Grains is a measure of wt. There are 7000gr in a pound. In factory ammo, it refers to the bullets weight. The heavier the bullet the lower the powder charge & the lower the vel. Foot#s of energy will increase faster w/ the increase of vel than if you increase bullet wt. What does it all mean to the plinker or target shooter, not much. It's only mildly relavent to the defensive shooter too. The higher the vel the more likely it is a JHP will expand. The heavier the bulelt, the deeper it will suually penetrate.
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Old 02-01-2010, 19:15   #3
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Quote:
Originally Posted by fredj338 View Post
Grains is a measure of wt. There are 7000gr in a pound. In factory ammo, it refers to the bullets weight. The heavier the bullet the lower the powder charge & the lower the vel. Foot#s of energy will increase faster w/ the increase of vel than if you increase bullet wt. What does it all mean to the plinker or target shooter, not much. It's only mildly relavent to the defensive shooter too. The higher the vel the more likely it is a JHP will expand. The heavier the bulelt, the deeper it will suually penetrate.
Thank you very much... I get it now... the bullet is all the grain talk. after understanding that, it all makes sense! Thank you so much!
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Old 02-01-2010, 20:15   #4
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Just an FYI - You weigh powder charges in grains as well, but it doesn't sound like you're there yet...

Hope to see you back here when you've done some reloading homework and you're shooting your own loads!
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Old 02-01-2010, 20:39   #5
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Quote:
Originally Posted by oISHUTupNrocKIo View Post
Thank you very much... I get it now... the bullet is all the grain talk. after understanding that, it all makes sense! Thank you so much!
Don't think you do yet. Grains are a unit of weight. Projectiles are measured in grains as is the amount of powder in the round.

When you buy commercial ammo, the grains refers to the weight of the projectile (they don't tell you how much powder is in the case - ie how many grains of which powder).

You can increase the powder (ie more grains) and get more velocity, or you could (if you reloaded) use a lighter projectile (ie less grains) and get more velocity.

It's all a question of balancing variables.

The book "ABC's of Reloading" would answer a lot of questions for you.
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Old 02-02-2010, 00:48   #6
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Originally Posted by dudel View Post
Don't think you do yet. Grains are a unit of weight. Projectiles are measured in grains as is the amount of powder in the round.

When you buy commercial ammo, the grains refers to the weight of the projectile (they don't tell you how much powder is in the case - ie how many grains of which powder).

You can increase the powder (ie more grains) and get more velocity, or you could (if you reloaded) use a lighter projectile (ie less grains) and get more velocity.

It's all a question of balancing variables.

The book "ABC's of Reloading" would answer a lot of questions for you.
I think he was just looking for the explaination from a factory ammo view point, at least that is how I read it. For those used to buying SG ammo, the grains/bullet wt. thing is questioning. SG shells tell you the powder charge, metallic cartridges the bullet wt. Birdshot gets bigger as the numbers get smaller & buckshot gets smaller as the numbers get bigger, etc. I can see how newbs get confused.
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Old 02-02-2010, 02:47   #7
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Quote:
Originally Posted by fredj338 View Post
I think he was just looking for the explaination from a factory ammo view point, at least that is how I read it. For those used to buying SG ammo, the grains/bullet wt. thing is questioning. SG shells tell you the powder charge, metallic cartridges the bullet wt. Birdshot gets bigger as the numbers get smaller & buckshot gets smaller as the numbers get bigger, etc. I can see how newbs get confused.
Not to mention drams
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Old 02-02-2010, 07:25   #8
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Formula to find Foot Pounds of Energy

FPS x FPS x Grains divided by 450240 = FPE


Feet per second x feet per second x grains of bullet divided by 450240 = foot pounds of energy.


For the 180 grain bullet,

1350fps x 1350fps x 180gn = 328050000

Divided by 450240 = 728.6 FPE


For the 200 grain bullet,

1200 fps x 1200 fps x 200 = 288000000

Divided by 450240 = 639.6 FPE

Bob


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Old 02-02-2010, 10:22   #9
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This might help playing with the variables of velocity and bullet weight.
http://www.larrywillis.com/bullet-energy.html
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