Grain?

[CicciLaPorta]

I understand that the grain number on a box of ammo has to do with the weight of the bullet. I don't understand the importance of this number though. Can anyone explain in layman terms why this number matters?

[Sleighter]

I am not a ballistic expert, but there are some general rules of thumb regarding bullet weight and if I'm wrong someone will be along to correct me.

Something to always remember is "lighter is faster, heavier is slower". Faster isn't always better.

Handguns: Generally in handguns you'll have 3 or 4 different bullet weights per caliber. Within each caliber I find that the lighter bullets tend to have more sharp recoil, while heavier bullets have more of a "push" type of recoil.

For competition there are power requirements for each caliber so there are reasons to go heavier or lighter depending on your need. Furthermore, for self defense (hollow point loads) there are pros and cons to lighter or heavier bullets.

Long Rifles: When you start dealing with longer ranges are when you really start to see variations in bullet weights. Lighter (faster) bullets will have less vertical drop per 100 yards than a heavier, slower bullet. However, a heavier bullet will be less effected by wind and so will have less horizontal variation with different wind conditions. Also, heavier bullets will generally penetrate further due to their higher mass.

Now there are tons and tons of variables that go into ballistic performance. And like I said, I'm not an expert. But luckily we do have some ballistic experts here, so stick around and you'll find all the answers you're looking for.

[barrage]

KE = 1/2 * m * v^2

[Sutcliffe]

why does it matter?

Not sure it does. It is a unit of measure and represents 1 seven thousandth of a lb. Meaning a 700 grain bullet(something like a .50 BMG) weighs a tenth of a pound.

Helpful?

They also measure powder in grains as well.

[Webologist]

I understand that the grain number on a box of ammo has to do with the weight of the bullet. I don't understand the importance of this number though. Can anyone explain in layman terms why this number matters?

1 Grain = 1/7000 Pound

Why it matters is hard to describe adequately in a short response. Consider this gross oversimplification the tip of the iceberg.

A lighter bullet can typically achieve higher muzzle velocity for a similar pressure. Many factors play into this, including powder burn rate, powder charge, barrel length and case capacity.

Flight characteristics are also impacted. Bullets, regardless of weight, for a specific caliber have the same diameter, thus the same frontal area. The shape of the bullet affects the ballistic coefficient of the round. Heavier rounds can be longer and more aerodynamic given a similar design. They also carry more momentum. This means that heavier bullets usually lose less velocity over a given distance, despite leaving the barrel at a lower velocity relative to lighter bullets.

When the bullet hits the target (terminal ballistics) velocity,bullet weight and design determine expansion and penetration of the target. Handgun rounds typically have more reliable expansion at higher velocities. Heavier bullets typically penetrate deeper for a given level of expansion and velocity. Over-penetration and under-penetration are both typically considered undesirable. As a result, cartridge manufacturers offer rounds with weights, shape, construction and velocity optimized for each caliber and application. (Shooting paper at long ranges, gophers at long range, charging brown bear, steel plate, etc.)

[CicciLaPorta]

Thanks to everyone. I understand now. At my limited shooting experience,band the fact that I only shoot handguns and shotguns, that grain number is of little consequence whe n I am selecting box of ammo to take to the range. Thanks again!

[CaliforniaLiberal]

I've got just one word for you. Ballistics.

http://en.wikipedia.org/wiki/Ballistics#Subfields

[-hanko]

Thanks to everyone. I understand now. At my limited shooting experience,band the fact that I only shoot handguns and shotguns, that grain number bullet weight is of little consequence whe n I am selecting box of ammo to take to the range. Thanks again!

Fixed, as you probably don't call your weight your "pound number"...I hope.

[CicciLaPorta]

Fixed, as you probably don't call your weight your "pound number"...I hope.

As a matter of fact, I do.

[hermosabeach]

So Light and Fast deliver a ton of energy.....

Light and fast also helps to break a bullet up into tiny fragments...

Tiny Fragments don't penetrate as much
But when a bullet stops in the target- 100% of the energy is transferred into the target....


Tiny fast bullets also slow down faster.... you can throw a feather fast, but as it has little mass, it slows rapidly....

Tiny bullets bust up and don't penetrate the shoulder on a big animal...


With handguns, you have a similar situation.... but not as extreme as rifles due to the higher velocities found in rifles... so the Velocity Squared is a much bigger number with a 2,800 FPS .308 over an 900 FPS .45 ACP.


People are thin skinned so the 115/124 Grain 9MM is common with self defense ammo. The ammo has enough speed to expand a hollow point....

For Wild Pigs, the 180 grain lead .357 load is awesome as it has the density to punch through bone in order to get to the vital areas....


I tried to keep my reply more real world and examples than math.


What is your #1 round that you shoot and what would be a real life example of a target? If you state this, we could hone in on and example that might be more relevant to you

[CicciLaPorta]

I shoot a 9mm handgun, usually at cardboard. For this I normally use 115 grain fmj. I bought a small box of hollow points for HD that are also 115 grain. But I never knew what the number meant.

[NIKSD]

I shoot a 9mm handgun, usually at cardboard. For this I normally use 115 grain fmj. I bought a small box of hollow points for HD that are also 115 grain. But I never knew what the number meant.

Like the people said above, 115 grain is the weight of the bullet /projectile/. 115 grain in 9mm is the most common weight bullet. If the gun is your HD firearm, you may consider Federal HST HP 147 grain /heavier projectile/ for home defense. Buy several boxes, run some of the HST, just to see if your gun likes them, keep the HST loaded mags for HD /i have at least 2 per gun loaded all the time and strictly for HD/, and use 115 for range.

Theoretically you should use same grain loads for the range and home defense, but this idea gets very expensive very fast.
When you are going to test your HD ammo, test it on a dirty gun /run some range ammo, when done shooting for the day, run the HD expensive ammo for reliability test/.

I hope this helps.
Not an expert, just amateur opinion.

[Rottentofu]

I have always wanted to ask this question but felt kinda dumb doing so. But since this thread is created I figure I might as well...

When I compare my 125g 9mm to my 55g 5.56mm, the 5.56mm bullet (not the casing) seems so much bigger...

[-hanko]

I have always wanted to ask this question but felt kinda dumb doing so. But since this thread is created I figure I might as well...

When I compare my 125g 9mm to my 55g 5.56mm, the 5.56mm bullet (not the casing) seems so much bigger...

No question is dumb...though some of the answers might be.

The .223 bullet is longer, but the smaller diameter makes it weigh less than the 9mm bullet. Remember that calibers are designated by nominal bullet diameter, not bullet length.

[Decoligny]

Not sure it does. It is a unit of measure and represents 1 seven thousandth of a lb. Meaning a 700 grain bullet(something like a .50 BMG) weighs a tenth of a pound.

Helpful?

They also measure powder in grains as well.

Good God, I weigh One and Three Quarters of a Million Grains!!!!!!