In Need Of a Bullet Grain Education - Suzuki GSX-R Motorcycle Forums Gixxer.com
 
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post #1 of 8 (permalink) Old 10-03-2012, 09:18 AM Thread Starter
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In Need Of a Bullet Grain Education

Can someone or two explain the reason you would chose a certain “GRAIN” of bullet over another. And what grain you prefer? I currently own several firearms (Glock 23, Sig 2022, DPMS 5.56/.223, XD 40 and an old Squire 22 rifle). Up until I purchased my AR about 2 months ago it really didn’t pay attention to the grain of bullet I was purchasing.
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post #2 of 8 (permalink) Old 10-03-2012, 10:30 AM
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Re: In Need Of a Bullet Grain Education

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Originally Posted by E_Dub View Post
Can someone or two explain the reason you would chose a certain “GRAIN” of bullet over another. And what grain you prefer? I currently own several firearms (Glock 23, Sig 2022, DPMS 5.56/.223, XD 40 and an old Squire 22 rifle). Up until I purchased my AR about 2 months ago it really didn’t pay attention to the grain of bullet I was purchasing.
Okay this got very long. Quick scan the bolded parts if you're in a hurry.

The short answer is ballistics. Of course, the science of ballistics is something in which you can practically get a university degree and still not really cover it very well. Which is to say, I'm no expert and what I'll post here are extraordinarily basic. :-)

In-flight ballistics is about how a bullet performs in flight between the time it exits the muzzle of the barrel and the time it impacts the target. Terminal ballistics is the science of what happens to the bullet at impact until it stops.

"Grains" is a measure of the weight of the bullet. There are 7000 grains in a pound, not that that is necessary unless you're reloading and casting your own and need to calculate material requirements.

There is no such thing as the ballistics of a bullet in and of itself. All other factors of the shot have to be taken into effect in order to be able to determine what is about to happen. The twist rate of the barrel has a lot to do with the flight of the bullet. A heavier bullet will perform differently than a lighter bullet. Indeed, a bullet that is spinning too fast for it's weight can actually disassemble during flight! Ergo, use the right bullet weight for your twist rate. You'll need to let us know the twist rate on your AR in order to give you any recommendations.

Velocity has a lot to do with ballistics. Heavier bullets are generally loaded "hotter" and will travel faster but it may or may not be a benefit. Other variables have an effect as well.

As the distance to the target increases, various variables which seem minute will have a more profound effect on where the bullet impacts the target. On a pistol range at 21 feet, even a fairly fast breeze will not have a huge effect on the in-flight ballistics of the bullet but at 1,000 yards, a slight breeze can knock you off target quite significantly. So can the temperature, the variance between the temperate at which the cartridge was loaded vs. the temperature where you're shooting, whether or not you're shooting downhill or uphill, whether or not your barrel is still hot from the last shot, still dirty from the last shot. Even the coriolis effect of the Earth's rotation can have an effect on very long shots.

Okay, more than you wanted to know, I'm sure. All of the above relates, of course, to in-flight ballistics and again, it's definitely not complete.

Terminal ballistics, as mentioned, relates to what happens to the bullet as it hits the target and travels through it or stops within it. In recent years, bullets have been designed with an increasing focus on this area of the science. In other words, bullets are increasingly "purpose built." Get the ones that suit your requirements, considering purpose for the bullet, gun to use it in, size of bullet, sometimes even the climate and weather conditions.

If you're buying bullets for hunting purposes, the terminal ballistics aspect is critical for you. If you shoot a bullet into an animal and the bullet is ball ammo, it's just going to go right through and do very little critical damage and the animal will have a high risk of running away injured but very much alive. On the other hand, if you use an expanding bullet to shoot a bear in the head, it's more likely to bounce off his skull and piss him off and if he leaves you alone afterward, you're lucky. If he doesn't you're not. Ball ammo in this case might be far superior as it can penetrate bone and skull more effectively.

FBI and police agencies put some real effort into making sure their ammo is not going to over penetrate bad guys and continue in a flight patter that is a risk to innocent bystanders. The idea is to make sure the bullets stop inside the bad guys to eliminate or minimize the over penetration risk. You should consider such questions when buying your own self-defense ammo.

Again, very basic.

--Wag--

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post #3 of 8 (permalink) Old 10-03-2012, 02:28 PM Thread Starter
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Re: In Need Of a Bullet Grain Education

Thanks for the details. My AR has a 1-9 twist barrel. I had to read it over briefly because I am at work. I will read in depth when I get home.
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post #4 of 8 (permalink) Old 10-03-2012, 02:55 PM
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Re: In Need Of a Bullet Grain Education

That's a fairly typical (fast) twist rate so you should be able to use heavier bullets. And shoot at longer ranges as a result. Nevertheless, a well-constructed, lighter bullet will likely do just fine.

Bullet construction is going to have an effect as well so you'll have to do some homework on that too. Hollow points are said to have better aerodynamics, too, so you may want to start there.

Last but not least, let us know what you're trying to accomplish and that will help, too.

--Wag--
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post #5 of 8 (permalink) Old 10-04-2012, 11:05 AM Thread Starter
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Re: In Need Of a Bullet Grain Education

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That's a fairly typical (fast) twist rate so you should be able to use heavier bullets. And shoot at longer ranges as a result. Nevertheless, a well-constructed, lighter bullet will likely do just fine.

Bullet construction is going to have an effect as well so you'll have to do some homework on that too. Hollow points are said to have better aerodynamics, too, so you may want to start there.

Last but not least, let us know what you're trying to accomplish and that will help, too.

--Wag--
I've only been able to utilize the local indoor shooting range that goes out to 25 yards. I will be able to shoot at a longer distant when I go home to visit my mother in Florida in a couple of weeks.
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post #6 of 8 (permalink) Old 10-04-2012, 01:44 PM
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Re: In Need Of a Bullet Grain Education

Something else to consider is that different guns shoot differently, no matter what ammo you use. In other words, I can take a box of ammo and shoot half with one gun and half with another and get vastly different results.

True story: Years ago, we bought a pair of Sig P220's which were five numbers apart on the serial numbers. One would shoot tight groups with one box of ammo and the other wouldn't hit the broad side of a barn, relatively speaking. Try a different box, different brand and the results were reversed.

I load my own most of the time and it can get to be intriguing to figure out how a great load for the GP100 sucks in the 586 and vice versa. Same with the loads in the Beretta 92FS vs. the P89DC. You just never know what a gun is going to like.

After all is said and done, whatever you read is going to be strictly anecdotal. The best you can get is a starting point and then, after trial and error, you'll be able to figure out what your guns like and if you're shooting long range, you'll be able to figure out the math that works for YOUR rifle. Best advice I can give you in any case is keep meticulous records.

And have fun!

--Wag--

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post #7 of 8 (permalink) Old 10-05-2012, 10:41 PM
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Re: In Need Of a Bullet Grain Education

My AR also has a 1/9 twist barrel, and find that I get my best groups out of 69 grain.
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post #8 of 8 (permalink) Old 10-07-2012, 09:58 PM
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Re: In Need Of a Bullet Grain Education

The only thing I didn't see mentioned for OP is that one more factor in finding the best load for YOU is also wind & any possible branches, etc. The lighter (less grains) the bullet, the easier it will be deflected.
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