Heavier/slow bullets vs faster/light bullets

[flap]

Hi all,

This is just an academic question for my information. I'm not trying to achieve anything in particular. These numbers won't be anything like reality, just using simple ones for the example...

Say you have a rifle in calibre X.

You can shoot either a 100gr bullet at 1000fps

or you can shoot a 90gr bullet at 1,100fps.

10% lighter, but 10% faster.

What would make you choose one over the other?

[yoshie]

I think the answer to this question is function.

What is the intended purposes?

Take hunting as example... Small animals that will be dispatched with a light bullet from a distance with a lasor trajectory vs a large 4 legged animal that requires deep penetration to reach vital organs that is engaged from close.

[Blackened]

This is painting with a broad brush, but in general.

Lighter/faster pills shoot shoot flatter which make them easier to use as there is a lesser rate of drop over distances.
A lighter pill will put up less resistance to the rifle firing it and so will have less recoil.

Heavier pills will typically hit with more energy, even though they are moving slower. Mass in most cases has a greater effect on this than velocity.
A heavier bullet of the same design will be longer which, all else being equal, should normally give it a higher ballistic coefficient

This is real general rule of thumb stuff though... In reality any of the above might not actually apply depending on the situation.

[Monty]

What blackened has said is pretty on the money if you're talking about the same family of calibres. Comparing a .270 vs .308 for example.

If you throw magnums into the mix though it all goes out the window.

e.g. a .270 WSM with 150gr bullets will shoot flatter AND hit harder than a .308 with 180gr bullets despite the lighter bullet.

On the flip side, a 300 win mag would hit harder AND shoot flatter than a .270, despite the lighter bullets.

[tucked]

All interesting, but I suppose at the end of the day it's all irrelevant right?

Like yoshie says, if you're shooting bunnies you buy one of a couple of small calibre options which all do the job, and if you're shooting deer you buy one of a couple of large calibres which all do the job?

[5Tom]

Bullet weight is determined by the Barrels rate of twist. You can have different twist rates between two different rifles of the same calibre therefore one barrel may be more accurate with a 90gr projectile and the other may be more accurate with a 100gr projectile. If you ever get into hand loading, there will be so much more that you'll find out about and how every factor intervenes with a different factor, just for the sake of accuracy.

As the others said, the mass and speed of a projectile is determined by the impact energy needed for a quick, humane kill.

[Supporter]

Say you have a rifle in calibre X.
You can shoot either a 100gr bullet at 1000fps
or you can shoot a 90gr bullet at 1,100fps.
10% lighter, but 10% faster.
What would make you choose one over the other?

The guys have covered the tech stuff pretty good.

In terms of choosing for practical use between bullets like you've asked above, for bigger game you would choose the bigger bullet.

For smaller game you'd take the flatter shooting, lower recoil one.

[bunnybuster]

In a 243 for example, a 90-100 gr projectile would be suitable for pigs etc. shooting through grass and light foliage.

A 70-75 gr projectile in contrast can be driven faster, will despatch foxes decisively, but is too light for pigs and will break up on twigs and grass, and will not arrive on target.

Be safe,
BB

[BBJ]

Following BB's comment, the guys who go for really high velocity and are just out to bust bunnies often go even lighter on the bullet weight.

They can get some screaming velocities out of a 55gr pill in a .243 that shoots about as flat as can be.

[flap]

Thanks for the feedbank guys. Appreciated.