Bullet Grain Questions

[Echo9]

Hi, I'm new here. I'm not actually interested in reloading yet, (no way I can afford it) I just had some questions I thought you guys in the reloading section specifically could answer.

Now I'm definitely not new to guns.... In fact I sell them. But the more I learn about guns, the more questions I have.

I'm asking specifically about grain. I understand that grain is bullet weight -- but what does that mean to the ballistics? I'd always been told that as grain goes up within one caliber, the bullet is heavier and so has more powder to push it at the same velocity as the grain below it. That appears to be wrong.

So how does it work? I know higher grains have shorter effective ranges, but besides that and bullet weight, what increases with grain? What decreases? How does grain affect muzzle energy? Terminal performance? I've seen charts, but there don't seem to be any patterns.

One more thing: How are you to know the length of the bullet in any given cartridge? I spent longer than I'd like to admit thinking that a 9mm Para bullet was 19mm long, .308 fired a 51mm long bullet, etc. I now know that the second dimension is actually the case length. But data on bullet length seems nonexistent. Isn't bullet length important to things like penetration and tendency to yaw in soft targets?

I'm not asking you guys to write a book here, but any information anyone feels like giving out (or linking to) would really be appreciated.

Thanks in advanced.

 

[Landric]

A grain is a measure of weight, there are 7000 grains in a pound, 437.5 in an ounce. How the individual bullet weight effects the cartridge varies quite a bit depending on what it is loaded in, the velocity, the shape of the bullet, etc.

The short version is basically the higher the number of grains listed, the heavier the bullet is. Powder is also measured in grains, but most modern cartridges make no reference to powder weight in their name. Older black powder cartridges often did, but while the names stayed the same when they were converted to smokeless powder, the charge weights did not.

 

[chris in va]

You don't have to spend a wad of cash if you just want to 'try' reloading. My entire setup cost me $120. Dies, loader, caliper, scale...everything.

Now I'm looking at casting my own bullets.

 

[bullseye308]

I'm asking specifically about grain. I understand that grain is bullet weight

First off there are 7000 grains to a pound.

but what does that mean to the ballistics? I'd always been told that as grain goes up within one caliber, the bullet is heavier and so has more powder to push it at the same velocity as the grain below it. That appears to be wrong.

Way too many variables depending upon caliber. Say for example 9mm, with a heavier bullet it doesn't have to move faster due to more mass. Adding more powder does not equate to more velocity in a linear fashion.

I know higher grains have shorter effective ranges, but besides that and bullet weight, what increases with grain? What decreases? How does grain affect muzzle energy? Terminal performance? I've seen charts, but there don't seem to be any patterns.

If you could pick a caliber this would be easier. Heavier bullets usually move slower or sometimes at the same speed. The length of the bullet increases with grain weight, the diameter is set, so if you add weight it adds into the length. Bullet weight and velocity determine muzzle energy. There aren't really patterns unless you look at one caliber.

One more thing: How are you to know the length of the bullet in any given cartridge? I spent longer than I'd like to admit thinking that a 9mm Para bullet was 19mm long, .308 fired a 51mm long bullet, etc. I now know that the second dimension is actually the case length. But data on bullet length seems nonexistent. Isn't bullet length important to things like penetration and tendency to yaw in soft targets?

The length of the bullet itself is not all that important. The overall length of the loaded cartridge is what you are looking for. Different styles and weights of bullets will have different lengths.

I'm not actually interested in reloading yet, (no way I can afford it)

Like mentioned above, you can get into it for very little to start off. If you shoot a lot and have time for another hobby, you can definitely afford it.

 

[Lee Roder]

well, a long time ago, a grain (literally of wheat iirc) was taken as a unit of mass. in metric 1 grain is approximately 65 milligrams.

muzzle velocity depends upon the energy imparted to the bullet by burning a given mass of powder to propel it down the barrel and upon the mass of the bullet itself. for a given charge, the product of bullet mass times the square of its velocity is constant. so increasing bullet mass lowers bullet velocity and vice versa.

a bullet's "length" is proportional to its ballistic coefficient which is generally listed in the manuals. an arrow has a much higher ballistic coefficient than does a spherical form of the same mass.

 

[dmazur]

Welcome to THR.

Here's some reading to get you started -

http://en.wikipedia.org/wiki/Bullet

http://en.wikipedia.org/wiki/External_ballistics

http://en.wikipedia.org/wiki/Muzzle_energy

Here's some reload data from a site I found -

.30-06 Springfield

150 grain Hornady SP InterLock bullet, 58.0 grains IMR 4350 powder, Federal 210 primer, Hornady brass. MV 2900 fps in 23.75" barrel. (Based on the Hornady Handbook, Sixth Edition.)

165 grain Hornady SP InterLock bullet, 55.8 grains IMR 4350 powder, Federal 210 primer, Hornady brass. MV 2800 fps in 23.75" barrel. (Based on the Hornady Handbook, Sixth Edition.)

180 grain Hornady SP InterLock bullet, 54.5 grains IMR 4350 powder, Federal 210 primer, Hornady brass. MV 2700 fps in 23.75" barrel. MAXIMUM LOAD! (Based on the Hornady Handbook, Sixth Edition.)

You will note that the powder charge and velocity go down as the bullet weight goes up. While it is possible to select different powders and load for a lower velocity than shown, it is generally true that within a reasonable pressure limit, higher weight bullets are loaded to lower muzzle velocities with less powder than lighter weight bullets (in the same cartridge.)

 

[chris in va]

The length of the bullet increases with grain weight

Well, sortof. A 115 JHP will be shorter than a 115 FMJ. Just splitting hairs a bit.

 

[suemarkp]

Bullet length depends on its weight and material. A Barnes copper "X bullet" will be longer than a pure lead bullet of the same weight and caliber because copper/zinc is lighter than lead. Pure lead isn't always used, usually there is some percentage of tin or antimony. These weigh less, so the more of that the longer a bullet will be for the same weight and caliber. Jacketed bullets have a copper jacket. Depending on the thickness, that will add length as copper is lighter than lead.

The stability of a bullet depends on its speed and length in calibers. Longer bullets must be spun faster (so either a faster rifling twist or more velocity). A 1-7 rifling twist is 1 turn in 7". This is faster than a 1-10 twist. Typical rilfing twists are 1-7 for heavy bullet .223's, 1-14 for light bullet .223, 1-10 for .308 Win, 1-20 for .458 Win Mag.

 

[qajaq59]

Now I'm looking at casting my own bullets.

Chris.... Go for it!! You'll learn a lot, have fun and save money.

 

[Walkalong]

A reloading book would be a super investment. You'll need it one of these days anyway. It will answer a multitude of questions, as well as give you even more, but better informed questions.

 

[Echo9]

Sorry for the delay in replying.

Wow, thanks for your replies everyone. Really helpful. I know you guys spend your time on here discussing more interesting stuff that is currently way over my head, so I appreciate all of you taking the time to explain basic stuff. The tendency toward courtesy and respect is why I picked THR.

Anyway, as I said before, the more I know, the more questions I have. So...

One thing I'm wondering is what characteristics determine whether a bullet yaws in soft targets, like a 5.56 or 4.6 does (or is supposed to). I'm assuming higher grain (because as grain goes up, so does length) and the weight distribution of the bullet. Is that right? Or is there more to it? I know someone said bullet length isn't that important, so I'm a little confused. Yawing seems pretty destructive.

What yields greater penetration (soft or hard targets)? Higher or lower? I’m speaking very generally here, I understand it may differ across calibers.

One more question. Very generally speaking, does lower grain normally translate into more felt recoil? Considering that there’s more room for powder with a shorter bullet, and the way people refer to one load being "hotter" than another, that seems to be the case.

And again, I know that's a pretty tall order, so I won't ask you to personally write me a reloading manual (which I'll be picking up). Any information you could pass on would be appreciated.

 

[dmazur]

Very generally speaking, does lower grain normally translate into more felt recoil? Considering that there’s more room for powder with a shorter bullet, and the way people refer to one load being "hotter" than another, that seems to be the case.

Here's a recoil calculator you can experiment with -

http://kwk.us/recoil.html

Generally, recoil goes up with increased bullet weight in the same cartridge. While the weight of the powder charge is part of the recoil equations (as it is part of the "ejecta"), decreases in powder are more than offset by the increase in bullet weight for typical loads. Using the .30-06 loads I referenced above, the 150gr load uses 58gr of powder and the 180gr load uses 54.5gr of powder. The 180gr load ejecta is larger than the 150gr ejecta, so (for the same weight rifle) it is likely going to produce more recoil. You have to run the formula to be sure...

 

[BADUNAME37]

What you are interested in is the most streamline bullet to do the job.

You need to look at the bullet's Ballistic Coefficient. As for the yaw, it relates to the weight of the bullet and how that weight is distributed in combination with how fast the bullet is spinning. Remember, a lot of rifle bullets are spinning faster than 200,000 RPM's! Do you realize how much energy just the spinning puts off?

Drop that into a room, without even shooting it and it would be literally flying around just from the spinning!

A .223 (5.56 NATO) does what it does, 99.99999% of the time, because the base of the bullet is heavier than the nose, so the bullet wants to turn itself around, so it will eventually be going backwards. It does not do that until something upsets the spin and the bullet itself. The bullet hits gelatin, water, wood, metal, you name it, and that particular bullet starts to flip around to go in reverse, all the while it is spinning at extremely high speed (you can figure out how fast the spin is by knowing the twist rate of the weapon, typically 1:9 for a .223, and the speed of the bullet). In this example, for every 9", the bullet is spinning one revolution.