More powder for smaller grain bullet?

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wiiawiwb

wiiawiwb

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New to reloading and I've thus far reloaded only 45LC and things are going well. I've decided to try reloading 454 Casull and was looking at the load data in my Lymans 49th Edition.

A 255 grain cast bullet (#452490) calls for 14.7 starting grains while a 325 grain cast bullet (#452651) calls for 11.3 starting grains.

Why would a smaller grain bullet need more grains of powder than a larger bullet?
 
I've puzzled through this very question myself.
It has to do with pressure. A heavier bullet creates the same pressure with less powder because it's harder to get moving.

Some one much more knowledgeable than I will be along soon, I'm sure.
 
The physics of it is counter intuitive. It seems that it is pressure which pushes a bullet in order to release it from the case. If I were in a room with a closed door which I wanted to open outward, it would take more energy for me to push the door open if a fat guy were leaning against it than a skinny guy.

Why isn't it the same with a bullet?
 
Generally, the heavier the bullet, the deeper it gets seated. Therefore, the deeper it gets seated, the less volume is left in the casing for the powder. With less volume, it takes less powder to increase the pressure.
 
A heavier bullet both occupies more internal volume, and also starts slower, thus allowing less powder to create and maintain typical and necessary peak pressures. If you were to use more powder with the heavier bullet, it wouldn't exit the cartridge quick enough, thus peak pressures would go above red line.

Where as the opposite is true with a lighter bullet. The bullet moves easier / quicker, and there is a larger void inside the cartridge, so it requires more powder to reach and maintain a typical or necessary peak pressure. And it would also experience an incomplete or inefficient burn with a reduced charge intended for the heavier bullet.

It's really a timing thing.

GS
 
Hate to confuse the issue even more, but seating depth is not the only factor.
And usually not even the biggest one.

Gunpowder acts far different than an initial push at a door, it's more like letting pressure out of your air compressor.;)
 
The answers to both of your latest threads are basics that are covered in every reloading manual. Asking questions is great, but there is no substitute for the base knowledge gained from reading a good reloading manual. Every foundation needs a good base. :)
 
For what it is worth, I pulled out my Lyman's 49th Edition with the express purpose of trying to find the answer to this question. I couldn't find it. If it's there I can not ferret it out.

With all due respect, by vocation I work with tax law. Complicated tax law with piles of digital books. I field many questions on tax forums and never discourage questions by asserting that all the person has to do is read the law, regulations, revenue rulings, revenue procedures, and court cases more carefully because, after all, it's all there if you just look for it. Speaking from experience, it is very easy to skip over even the most basic concepts.

When a person is first leaning about any new subject matter, issues are swirling around like an endless vortex and there is no base experience from which to draw upon. I can tell you that, sometimes, it is difficult to see the forest through the trees. Pick up a book and find the answer. Sure, that works for many questions but as I mentioned above I could not find the answer even knowing it is there somewhere.

I believe it is better to ask and be safe/know than be concerned with reprisal for asking in the first place. Kindly accept my apology for accessing others here if it has been an undue burden for this forum.
 
After reading your trade,

You'll have zero issues loading .45LC or .454 Casull once you read through the basics, maybe even another manual or two as well. :)
 
I haven't had any issues loading 45LC but maybe you can share your expertise and recommend that other manual or two.

Interesting isn't it how there are hundreds, maybe thousands, of others on this forum who have asked questions about loading 45LC and 454 Casull. According to you, had they only read those manuals you alluded to, there would have been no questions on this forum about 45LC or 454 Casull because there would have been zero issues.

That cheerfully encourages participation.
 
wiiawiwb said:
For what it is worth, I pulled out my Lyman's 49th Edition with the express purpose of trying to find the answer to this question. I couldn't find it. If it's there I can not ferret it out.

With all due respect, by vocation I work with tax law. Complicated tax law with piles of digital books. I field many questions on tax forums and never discourage questions by asserting that all the person has to do is read the law, regulations, revenue rulings, revenue procedures, and court cases more carefully because, after all, it's all there if you just look for it. Speaking from experience, it is very easy to skip over even the most basic concepts.

When a person is first leaning about any new subject matter, issues are swirling around like an endless vortex and there is no base experience from which to draw upon. I can tell you that, sometimes, it is difficult to see the forest through the trees. Pick up a book and find the answer. Sure, that works for many questions but as I mentioned above I could not find the answer even knowing it is there somewhere.

I believe it is better to ask and be safe/know than be concerned with reprisal for asking in the first place. Kindly accept my apology for accessing others here if it has been an undue burden for this forum.
Click to expand...
First and before all else I seriously doubt you are single handed able to burden this forum. All most members ask of the new hand loader is read the book, a book, any book. :) Sometimes the book in all its glory either answers your question in a way you do not understand or misses your question. Then come in here and ask and if you don't understand an answer ask again till you "get it". :)
Incidentally, you won't find bullet weight vs. powder charge in the Lyman 49th.
The only thing of importance is that you understand a question asked before leaving it. However, it's good practice to0 keep a line of question in a single thread. I saw this thread and thought I replied. Wrong! I replied to the question but in one of your other threads.
Taxes huh? My sister does personal and corporate tax. Confusing stuff, she does my taxes every year but I will never ask her to hand load ammunition for me. :)

Another manual? I like the Hornady 9th Edition and the current Speer manual. The powder manufacturers also have data online which is useful.

Ron
 
Thanks Ron for your helpful post. For what it is worth, I did read the Lyman 49th Edition before I ever went out and bought reloading equipment.

I think people who have reloaded for many years may forget what it is like when you have so many questions in your own mind about things you've never heard of. What's a crimp groove, annealing, cannelure, crimp jumping, slugging a barrel, etc, etc, etc. There is an endless parade of new issues.

To the uninitiated, like me, we're dealing with firearms and explosives which can ultimately cause harm, thus, we pay it great respect. I'd rather ask a question twice and be safe then not ask it and be unsafe. Everyone here has graciously offered their help and support and I both celebrate and applaud that.

By faithfully following this forum, reading manuals and other reference materials, and reloading more, I hope to one day add more this forum than I ask for. To pay back and reach out to those like me who were new and asked for help.

Until that day comes, I ask for your patience.
 
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Since Wikipedia can be edited by anyone it's not a great idea to use it as a highly scientific resource. But this article is pretty well written in my opinion. Skip down to the "Chamber" portion for the answer to your specific question.

https://en.m.wikipedia.org/wiki/Internal_ballistics

edit: I mixed something up. Don't skip to the "Chamber" section. Skip to the "Friction and Inertia" section and the subsection "The role of Inertia." But most of the article is worth reading if you find the physics of firearms interesting.
 
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I would be willing to bet that there is a fair number of reloader's who don't completely understand this. that said, we really don't need to understand this. If it's just a thing of curiosity, do some googling about cartridge designs and how they effect internal ballistics, should produce some explanation.

What one should realize, is that the experts have already figured it out for us, as such, they have provided the necessary facts in the form of load tables and pressure charts for us to follow and adhere to. In other words, we don't need to understand the in depth science involved in order to safely reload. In fact, I probably never gave this much thought myself until maybe 10 or 15 years ago. And even so, my understanding of internal ballistics is, and probably will remain rather vague and limited. But I don't need to understand the entirety of this particular aspect of internal ballistics, all I really needed to know is how to read the load tables, and learn the correct process of reloading, all of which is inside my books.

Just enjoy the hobby, let the ballistic guys provide the math for you.

GS
 
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It's physics where F=ma (F is Force, m is mass and a is acceleration).

So if you decrease mass, you need to increase acceleration to achieve same amount of force.

An example using 230 gr vs 155 gr 45ACP bullets and W231/HP-38 powder - http://www.hodgdonreloading.com/data/pistol

230 gr bullet uses 5.3 gr of powder to achieve 834 fps and 16,900 CUP of pressure.

155 gr bullet uses 6.7 gr of powder to achieve 1,112 fps and comparable 17,100 CUP.
Click to expand...

Of course there are other variables such as bullet type, seating depth, etc. but in general, you will need to use more powder with lighter bullet to produce same amount of chamber pressure.

I hope this helped.
 
First understand that max load is based on max pressure. Higher velocity is just a conseqence, not the goal, so powder charge is not based on "need" but rather the max amount you can put in there and stay within pressre limits.

Your powder charge generates pressure. Think of bullet weight as backpressure. Which puts more pressure on your wrist - shoving an empty shopping cart, or shoving a full one? If you shove an empty cart, and your wrists can handle the pressure of a full one, you can give it a harder shove (your increased powder charge) and have the same pressure on your wrists as the full cart but the cart will travel farther and faster. The lighter the bullet, the less backpressure which allows you to generate more pressure from your powder charge.

The deeper a bullet is seated, the more backpressure as well, and often times heavier bullets are longer and require a greater seating depth. You are generating the same volume of gases within a smaller space which means a higher pressure.
 
If I were in a room with a closed door which I wanted to open outward, it would take more energy for me to push the door open if a fat guy were leaning against it than a skinny guy.

Why isn't it the same with a bullet?
Click to expand...

A short answer to your question would be "it IS!" It is exactly the same with a bullet.

If you want your 325 gr. bullet to get up and move down the barrel at the same rate as a 255 gr. bullet, you're going to need to hit it with a lot more energy.

But think about that for a moment. How much energy (in this case, gas pressure) can your gun handle?

The reloading manual's load values are carefully worked out to keep you within safe pressures for your gun. That means that you can stuff a bunch of powder in behind a lighter bullet and get it going very fast, very quickly, without blowing up your gun -- BUT, when you switch to a much heavier bullet you have to back off how fast you demand that it moves. Try to blast it down the bore at the same acceleration and to the same velocity as that lighter bullet, and the energy required will likely blow your gun to bits.

That's why every reloading book will give lower charges, and lower maximum velocities for a given cartridge as you move toward the heavier bullets.

...

Back to your door analogy:

If there's nobody behind that door and you hit it hard, you'll blast on through without hurting yourself. If there's a big fat guy holding that door closed and you hit it so hard that you knock him back at the same velocity as you knocked back the door with nobody behind it? You're probably gonna DIE! :eek: :D
 
wiiawiwb, just FYI, your question about more powder for a lighter bullet is one of the most asked questions by new reloaders on reloading forums. It's a hard thing for most of us to grasp when first starting out. As you become more proficient and experienced, it will make as much sense to you as it does to those of us that have been reloading for years. Don't let the negative Nellies here keep you away anytime you have a question. Stick around and it won't be long till you are giving the advice to the newbies.
 
Hey Rule....I'm just asking for help. There are a thousand people every day who ask for something that has been asked a thousand times before. If asking for help is insulting to you, perhaps you might consider ignoring newbie posts like mine and focusing on discussions that hyper-experienced gun folks, like you, can enjoy.

I'm just trying to learn more and if that's wrong then I don't want to be right.
 
wiiawiwb said:
Hey Rule....I'm just asking for help. There are a thousand people every day who ask for something that has been asked a thousand times before. If asking for help is insulting to you, perhaps you might consider ignoring newbie posts like mine and focusing on discussions that hyper-experienced gun folks, like you, can enjoy.

I'm just trying to learn more and if that's wrong then I don't want to be right.
Click to expand...

I was not insulting you just saying that many others have asked the question and trying to give you some resources. I have helped many, many new reloaders on other forums and I am sure I have asked common questions when I started out also,

So, Don't Hey me. Hay is for horses. Lose the attitude.

I was trying to help you and gave you several links.so you could learn more about it,

Have no worries it will not happen again.
 
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