Why do some powders work better than other in certain chamberings?


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scythefwd
November 1, 2009, 05:33 AM
Guys,
I see suggestions that such and such powder works well in .308 win. etc. What causes a powder to to perform well in a chambering but not as well in other chamberings (say .308 win vs 30-06)? Please bear in mind that I am still getting my loading gear, so I have -1 year experience on reloading. I do have modern reloading rev. 2 and I have read it cover to cover.

1. Case length and shape? Does this matter and what does it effect? Angle of shoulder matter? Any details are wanted. Is case length a factor when choosing a powder? Is case shape (shoulder, taper, straight wall, etc) a consideration for what type of powder to use?

2. Powder burn rate? Why does the burn rate matter in accuracy? I know it matters for chamber pressure. Why does medium to slower powders perform better out of long actions than short actions (am I correct in this?) ?

3. Volume of powder? What makes a powder that takes 60gr to get 2600 fps more or less accurate than a powder that takes only 45 gr to get 2600 fps in the same rifle? I don't have any examples, but you guys get my point even if the loads aren't exactly doable.

4. Coarseness of powder? I know it matters in black powder, so I would suspect it matters in smokeless powders as well. Does it affect rate of burn only or are there other things to consider?

5. Any other factors you can think of.

And slightly off topic in my own thread :), why do some chamberings seem to perform better in general near their max loads and others do better backed off a bit (thinking belted mags vs. other here)?

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bluetopper
November 1, 2009, 08:22 AM
For in depth questions like this, especially if you're that interested (and that's great) my advice would be to go and purchase a reloading manual or two. Your questions will be answered a lot more fully and accurately than they will be here on this (with all due respect:)) rinky dink forum.

loadedround
November 1, 2009, 08:47 AM
Basically you have to match the powder to the case and bullet for best results...just like matching a tie to a new suit. Parasite is 100% correct in suggesting a good reloading manual such as the Lyman, speer or Nosler manual. All Your answers will be right there and correct.

ranger335v
November 1, 2009, 09:10 AM
"Why do some powders work better than other in certain chamberings? "

If anyone could answer that, he could make accurate predictions. Anyone who could make accurate predictions would make a fortune.

scythefwd
November 1, 2009, 09:11 AM
loadedroud / parisite... I have a reloading manual, just not the recommended ones. I understand that you have to get the right combo of bullet/powder/case for best results... what I am asking for is the whys of it. I will get the speer or hornady or lyman manuals... but for now I am looking to learn from the experience here. I am sure there are some benchrest shooters here that reload that could probably answer half of those off the top of their head without thinking.

scythefwd
November 1, 2009, 09:13 AM
ranger, there has to be some physics/math behind it... we just have to figure out what it is. I doubt the big companies are going out and shooting thousands of loads with mixed powders in order to work up a good load... they are taking educated guesses.

Galil5.56
November 1, 2009, 09:25 AM
....

psyop
November 1, 2009, 09:28 AM
but for now I am looking to learn from the experience here. I am sure there are some benchrest shooters here that reload that could probably answer half of those off the top of their head without thinking.

LOL...If you are looking for answers without thinking , the net is the right place.

If you want an answer born of decades of research and testing get one or 2,3,4 of the Recommended Manuals.

No offence intended...just Good Advice

scythefwd
November 1, 2009, 09:39 AM
psyop, I have already mentioned that I plan on getting a couple other manuals from the recommend reading. I bought the one that came most recommended to me, which was Modern Reloading rev.2 by Richard Lee. It doesn't answer the questions I have asked, which is why I am asking them.

RandyP
November 1, 2009, 09:51 AM
So basically you'd like a 4 year course in ballsitics and lifetimes of real world experience culled down to an internet paragraph or two?

That should prove challenging I reckon to the experts out there. Me, I just read the manuals and read everything else I can find on the subject. The library is also a great resource for books on the subject.

EDIT: I apologize if my answer sounds like I'm being a wise-a$$. not my intent. I know little enough about the subects you have raised to know that the answers to your questions are there (and they are legitimate questions) but the answers take a l.o.n.g. time to relate. Long enough to warrant entire sections of reloading manuals it turns out.

helg
November 1, 2009, 10:14 AM
When powder burns in the barrel, the pressure rises for around first 15% of the bullet travel in the barrel - the more powder is burned the higher the pressure becomes. Then, for the rest of the bullet travel, the pressure diminishes - volume for powder increases with the bullet travel, thus reducing the pressure faster than it raises due to powder burn.

Too fast powder raises pressure at the high level at the initial 15%, butrns completely when bullet is still deep in the bore, and for the rest of the travel no extra powder burns and accelerates the bullet. This decreases muzzle speed over a matching powder.

Too slow powder, at the opposite, can not raise pressure any way close to the max. It accelerates the bullet all the way through the bore, but not that intensive as the matching powder. In addition to slower muzzle speed, the slow powder gives significant muzzle flash, as it does not burn anyway close to 100% when bullet is in the bore.

This gives a clue why the matching powder has to be not too fast and not too slow.

I would recommend to check QuickLoad program. It is way less expensive than any ballistic course that you can find, and gives a good feeling of the above internal ballistics aspects. You can see with the program which powder could give the best performance in your gun with your bullet.

scythefwd
November 1, 2009, 11:23 AM
Randy, your not being smart butted. I agree, but I am trying to get the tip of the iceburg. If one person wants to do a summary... cool. Helg's answer is brief but useful. Thanks on that part H.

jfh
November 1, 2009, 11:40 AM
and at least a start on that for the layman can be found here (http://www.frfrogspad.com/intballi.htm).

I see "Mr. Frog" has reorganized his information recently; in its own way, this page was / is at least a place to start. I haven't chased this topic recently; it's more of a wintertime avocation for me. However, try googling for "internal ballistics" and look particularly for topics you find the point of view of physics.

When you find some useful links, post them in this thread--maybe we can get a resource together.

Jim H.

JimKirk
November 1, 2009, 11:53 AM
How can a member with 1000+ post not absorb some of the in depth discussions that take place on this forum. You should be able to answer a lot of your questions by listening to RC,ReloaderFred and their knowledge and there are many others on here with much more in depth knowledge than is displayed in most reloading manuals. There is a lot of info in those books, but a lot of such knowledge comes from doing and learning as you go.Like Randy said I don't want to come off as a wise a$$ either, I had to ask the above question. I have been reloading for 40+ years and I learn something new almost every time I log on to this or some of the other forums that I visit day and night. My suggestion to you is to READ READ READ!

Jimmy K

jfh
November 1, 2009, 11:54 AM
e.g., "...Why do some powders work better than others in certain chamberings?

As I alluded to in the first post, I think that certain recipes (not just powder) produce a complex reaction that optimizes all the variables that affect a given round.

These variables include the powder--with its burn rate, to name one variable--but also the case material (brass, its thickness, etc.), the bullet (you know the variables)--on back to the characteristics of the steel in the firearm's chamber / bolt / frame assembly--and the barrel length--and on and on and on. Now, throw in the 'physics' (and 'chemical') perspective for what happens when a propellant is ignited--and we begin to see how complex an analysis it is.

Some of these variables are arcane; others are "optimal" over a broad range a given analysis. As a result of the incalcuable number of tests done of the different combinations, and reported on, we learn which powders generally work well.

Which brings us to a second point: An understanding of how these variables interact really brings us back to a "statistical" perspective of a given recipe. IOW, each shot is an individual act, that fits somewhere into a curve of 'performance' of 1000s of other "identical" or similar rounds. (That's why we talk about SD or ES, or whatever, in chrono measurement.)

Have fun--there's lots of good brain-teasing to be had here.

Jim H.

WatongaJim
November 1, 2009, 12:37 PM
I had never heard of the QuickLoad software but after checking it out on their website, I'm going to add it my wish list. Really cool information.

ranger335v
November 1, 2009, 01:28 PM
"I doubt the big companies are going out and shooting thousands of loads with mixed powders in order to work up a good load... they are taking educated guesses. "

You are right of course, they don't do that. But then, neither do they concoct a "good" load in any sense except the velocity and pressure is right for the cartridge. A GOOD load is one that will do that plus be accurate. Thus, educated guess for what will be good load are little more than WAGS (wild-ass guesses).

Note that the reloading world is NOT beating a path to the doors of those who sell the various ballistics programs; there's a reason for that!

Perhaps anyone wanting to get anal about it in the office should get something like QuickLoad. But, bottom line, no program is really any better than a decent manual for predicting what a load will do. NO programmer can know or predict what my rifle - or yours - will respond to so fancy math calculations can only give us fancy math answers which, if were lucky, MAY come close to being correct. But, that's true of manuals as well, so....?

Better to spend the program money on components, load some experimental ammo, go to the range and see what happens.

helg
November 1, 2009, 02:01 PM
But, bottom line, no program is really any better than a decent manual for predicting what a load will do. NO programmer can know or predict what my rifle - or yours - will respond to so fancy math

There are certain aspects that make program better than manual.

1. Program gives you results for any load you ask. Manuals usually give only starting and max loads, the rest of the process is named "working up".

2. Manuals list specific bullets and OALs, and sometimes use only bullet weight to identify the load. Bullets, which have different design and length, but the same weight, and have to be seated to different OALs die to variations in design, are usually not distinctive in manuals. You may see how much this affects load results with the program. Water capacity of the case or bullet jump affect results of the internal ballistics a lot. These are not reflected in details in most manuals either.

3. Tolerances. Your powder measure is accurate to .1 grain, your OAL varies within .007", there are some other factors that vary in the load. How can you ensure with the manual that you do not exceed max pressure in the worst case scenario? Similar problem - how does these tolerances affect muzzle speed, and what variation in bullet drop, say, at 300yds, you should expect? Again, program gives answers, but manual does not.

4. Cast bullets. Some people are still using this. Unlike jacketed, cast bullets tolerate less interval of the chamber pressures. In fact, BHN of the cast bullet should match chamber pressure. Manual does not say what the load should be for the pressure that you need. The program does.

There are many other examples when the program can give you what manual can not. I am not a salesmen, but I really love the flexibility that the program gives over reloading manual. Or course, checking results of the program with loads, which are listed in a manual, should be the first step to get confidence in the program.

Carl N. Brown
November 1, 2009, 02:21 PM
Why does one .308 rifle shoot excellant with handloads using 4895 while another .308 rifle shoots excellant with handloads using 4350, but not vice versa? May be there are enough variables even within the same make and model of gun that each gun should be treated and tuned as an individual.

BullfrogKen
November 1, 2009, 02:23 PM
Lee's book discusses the answers to your questions in some detail.

Buy it. Read it.


It's just the way it is. Powders that both fully fill the case and are also near or at their maximum pressure/velocity perform more consistently. Certain powders just fit a family of calibers like a glove.

Richard Lee discusses why that is at some length in his book.

helg
November 1, 2009, 02:52 PM
Why does one .308 rifle shoot excellant with handloads using 4895 while another .308 rifle shoots excellant with handloads using 4350, but not vice versa? May be there are enough variables even within the same make and model of gun that each gun should be treated and tuned as an individual.

Slug your bore. Measure headspace, neck diameter, jump and the rest in your chamber. Load a round that is appropriate to the measures. Verify that the other gun of the same caliber has these measures different. Share your wows with the others here.

Making perfect ammo for a gun is multivariable optimization problem. The more you know of internals, the better result you can achieve.

ranger335v
November 1, 2009, 03:02 PM
"3. Tolerances. Your powder measure is accurate to .1 grain, your OAL varies within .007", there are some other factors that vary in the load. How can you ensure with the manual that you do not exceed max pressure in the worst case scenario? Similar problem - how does these tolerances affect muzzle speed, and what variation in bullet drop, say, at 300yds, you should expect? Again, program gives answers, but manual does not."

Taking just your point 3, how/why do you believe a program is any more informative/correct than a manual, even given the book's gaps? And many manuals do give ballistics tables, some out very far. But others don't bother because they KNOW such computed tables are little more than guesses past maybe 250 yards. Inside that distance, trajectory rarely matters.

A program certainly can't do any really valid projections largely because of the various tolerance differences you mention. In fact, that's a large part of WHY any such program is just a fancy WAG machine. Even the program's ballistic path projections are no more than approximations, partly because the B.C. changes in unpredictible ways as velocity changes. No one can program unpredictibles! Playing computer ballistics at home can be fun but it's little more accurate than most other computer games.

Therefore, the only way to know much of anything is to range test it.

dagger dog
November 1, 2009, 03:10 PM
Reading the history of the 22 Hornet ,2400 ( was it Herculese then) powder was designed for the Hornet with a 45 gr. bullet to give 2,400 fps. There are other similar round specific powders out there, but the Hornet is the only one that I can recall.

kelbro
November 1, 2009, 04:02 PM
There are a few who poo-poo the QuickLoad program and I don't know why unless they just don't want to part with the cash.

All external ballistics programs work off the same basic algorithms.

QL is an internal ballistics program and it has proven (to me) to be very, very close on at least 8 different chamberings. It also predicts which powders are 'most likely' to produce the best results. The savings in powder alone has more than paid for this program. It is just another tool to help arrive at that magic load. For me, it gets you there a little quicker and cheaper.

I know this doesn't answer the OP question but it does help to understand what's going on before the bullet leaves the muzzle.

Ky Larry
November 1, 2009, 04:20 PM
To fully understand why certain powder-bullet-case-primer-C.O.L. combos work the way they do would require several advanced degrees in physics, chemistry, and engineering. It is a study that can take as much or as little time as you want. Lots of fun and very informative.

Kernel
November 1, 2009, 05:27 PM
Question: Why do some powders work better than other in certain chamberings?
Answer: Thermodynamics

Cartridge performance is a function of three generic parameters: case capacity, bore size, and bullet weight. Neck angle, case length, and all that other stuff is just fluff for gun writers, add men, and blogs like this to expound on - they have very little real effect, some perhaps, but not much.

The concept of an “ideal powder speed” is a function of those three key parameters listed above and nothing else. The geometry of the cartridge and bullet seating depth come into play, but only in that they impact case capacity.

Link to an online Powley Computer that will do a lot of what Quckload will do, and costs you nothing:

http://kwk.us/powley.html

Sadly, the links to the supporting pages aren’t coming up today. Hopefully, that‘s a temporary issue they‘ll get corrected. There was a lot of good information there. (Update: all the links are working now).

Some of the math is explained on the Internal Ballistics Home Page:

http://www.mindspring.com/~sfaber1/

The scientific study of internal ballistics goes back to at least the 1880’s, when some of the best minds in physics, chemistry, and engineering worked for the military to develop the basic equations that are still used today in the simple thermodynamic models like Quickload, Load-From-A-Disk, and Powley‘s equations.

It’s funny. You can read some of these old text books and published papers that are over 100 years old, and you’d think you were reading from a recent copy of Handloader magazine. The basics haven’t changed. That’s not to say the science has stood still. The models that powder companies, ammo makers, and the military uses now are so advance it’s become nearly incomprehensible to the layman.

Walkalong
November 1, 2009, 05:29 PM
Just because. Some things ya gotta just believe. Who cares why. We could not predict it anyway. Most calibers have been around long enough that there are universally acknowledged powders that work well in most guns of that caliber.

helg
November 1, 2009, 05:37 PM
Taking just your point 3, how/why do you believe a program is any more informative/correct than a manual, even given the book's gaps? And many manuals do give ballistics tables, some out very far. But others don't bother because they KNOW such computed tables are little more than guesses past maybe 250 yards. Inside that distance, trajectory rarely matters.
Internal ballistics program, like QuickLoad, calculates what is happening before bullet leaves the barrel. Its XX century counterpart is loading manual. Both provide muzzle speed either to external ballistic program, like QuickTarget, or ballistic tables to calculate bullet drop. The tables do not answer what the variation of the muzzle speed to expect from the weight/OAL imperfections.

In the above example of .1 grain and .007" OAL - how do you find with the loading manual or ballistic tables do you need to buy better scale or take care of the OAL? Or you see that your chrony gives 20fps spread, is it because of powder, OAL or anything else? Internal ballistics program can help you to figure out where to look next. With "shoot-to-test" approach you may spend a bit more for better equipment just to figure out that it is neither powder weight nor OAL.
A program certainly can't do any really valid projections largely because of the various tolerance differences you mention. In fact, that's a large part of WHY any such program is just a fancy WAG machine. Even the program's ballistic path projections are no more than approximations, partly because the B.C. changes in unpredictible ways as velocity changes. No one can program unpredictibles! Playing computer ballistics at home can be fun but it's little more accurate than most other computer games.
I do not need to predict muzzle speed up to thousands of an inch per second. I do not need to know bullet flight path up to microns - you are right, there are too many factors to consider absolute accuracy. Good program, however, at this time gives way better accuracy in the external ballistics than published ballistic tables, and can resolve more in the internal ballistics than a loading manual can.
Therefore, the only way to know much of anything is to range test it.
Ultimate Scientist believes that everything, including bullet, rifle and powder, know The Laws of Physics and obey. The Laws are so good that no unrest can ever be thought of. Sancta simplicitas.

psyop
November 1, 2009, 06:03 PM
there are too many factors to consider absolute accuracy

Right On

scythefwd
November 1, 2009, 06:48 PM
jimkirk - the reason I haven't absorbed their knowledge is because I don't visit this subforum very frequently.

Bullfrog - I have Lee's book. Good read, I want more now.

JimKirk
November 1, 2009, 10:47 PM
Scythefwd
I really didn't mean anything by it. I just find it educational to visit most of the subforums on this site. Like I said, I read almost anything reloading-ballistics related, understanding is another matter

Jimmy K

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