Fast vs. Slow powder

[felix]

The idea, Charles, is to learn efficiently as possible, that's all. ... felix

[Char-Gar]

Hummm..Efficient learning? We have now moved beyond cast bullets to another level of living and thinking.

Efficient learning might mean short cut..maybe. I suppose a short cut is an "Ok" thing is it gets a fellow the correct place. Short cuts can also end up taking a fellow to the wrong place.

I practiced law long enough to have many folks plop their tails into a chair in my office and start telling me what the facts were. When it came to crunch time in the Court Room, many of these facts dissolved and became opinions, or assertions that could not be proved/verified.

When it comes to real world life, the only things that are true are the things that can be demonstration to be truth, to the folks that matter, when it matters. The things that prove to be true, collect the blue chips on the table. The rest of the things we call true, are just musing and ruminating.

Efficient learning.. well maybe..but I am not much into efficiency. I still work with hand tools when possible and consider the target as the ultimate decided of what works and what doesn't work.

For sure and for certain, I don't know as much as many on this board. But what I do know I have come by the old fashoned way...by experience.

I supose I have as many degrees as anybody on this board, and I do have respect for "book learning". But I have also learned that all books are not equal and not all are to be trusted or depended upon. The value of the book only has the value of the experience of the one who wrote it and the conclusions/theories he/she has drawn from that experience. Some times, folks draw erronious or partial conclusions.

I am all for efficient learning..sometimes! I am for collecting the blue chips all the time! When it comes to shooting, blue chip time (or not) is when you turn your target in to be scored. Thats all.

[oso]

I am for collecting fired boolits. Some are scrap and some speak to me. I have a filing system for those that speak to me (and I have different filing system for collectible targets.) If I have learned anything from this it's that the swimming pool test may be an efficient way to get fired boolits compared to what I have gone through. "Honey, we need a pool, I want to try something."

[Maven]

Questions: (1) Are the terms "compressive strength" and, for lack of a better term, "shear[ing] strength" of an alloy the same or at least correlated? (2) If an alloy has a high compressive (shear?) strength does it matter whether it is accelerated into the rifling at say 2 milliseconds with Red Dot or 10 milliseconds with IMR 3031? (The elapsed time I mentioned is merely for purposes of illustration and discussion.) In other words, was Richard Lee testing the effects of fast v. slow powders, or was he perhaps testing the strength of the alloy as well?

[38-55]

Maven,
You are on to what he was trying to get empirical data on. He was trying to discover at what point pressure damaged the bullet to the point of effecting accuracy. What he comes up with is a correlation between bullet strength ( or as he says 'ultimate compressive strength' ) and chamber pressure. I have messed around with his ideas and they appear to be valid. Kinda takes the intuitive voodoo out of casting alas... But it sure is interesting to know what to expect before hand rather than trial and error.. BTW Midway has his book on sale for 11 bucks... I really reccomend it.
Stay safe
Calvin

[Maven]

38-55, Thanks for confirming what I suspected. There was also an article by Steve Hurst, "Still More On Chamber Pressure And Brinell Hardness" in "The Fouling Shot" 131-10 that tries to deal with this empircally. The author provided these formulae:

BHN x 1,422 = tensile strength of the alloy in psi

BHN x 1,440 = minimum pressure [required] for obturatation

BHN x 1,440 + 10,560 = Maximum pressure a gas checked CB lube with Alox (sic) in a good (sic) bore will withstand.


Btw, I have the first edition of Lee's book and find the formula for obtaining a reduced load to be invaluable.

[38-55]

Maven Sir,
In Mr. Lee's second edition he converts over to psi so it is easier to correlate with the pressure data that is supplied by powder manufacturers. I know, myself being rather simple minded, any 'short cuts' in formulas is a big help.
I do know his explanation of the 'strength' of a bullet vs hard and soft bullets was a real eye opener for me. Sure makes sense once I grasped the point he is trying to make.. Good stuff all and all... Oh and my chronograph verifies his reduced load formula pretty well...
Stay safe
Calvin
PS Maven ya ever use his little lead hardness tester gizmo ?

[45 2.1]

BHN x 1,422 = tensile strength of the alloy in psi
Anybody besides me understand this formula.........??? The boolit is not under tension....!! It is under compression, its being pushed up the bore by powder gases. The tensile strength of lead is much, much less than its compressive strength. This is one of the reasons I consider this formula bogus.

BHN x 1,440 = minimum pressure [required] for obturatation

BHN x 1,440 + 10,560 = Maximum pressure a gas checked CB lube with Alox (sic) in a good (sic) bore will withstand.

[38-55]

45 2.1,
How would you quantify 'compressive strength' ? To me 'compressive strength' implies a certain amount of elasticity. This is the point that MR. Lee makes in his book... best accuracy ( what ever that may be ) "should" be achieved at or close to the 'ultimate compressive strength' of the projectile... He did come up with some interesting results as to how the application of pressure ( slow or fast) effects the bullet.
I'm not sure I agree with this while heartedly but he makes a interesting argument and lays out the way to test it. To me anyway it's just more knowledge in my tool box so to speak..
Stay safe
Calvin
PS The first formula is what it is but I really don't see the value in it..
As for the the other ones.. they seem arbitrary and don't seem to make any allowances for alloys... Just my 2 cents

[45 2.1]

45 2.1,
How would you quantify 'compressive strength' ? To me 'compressive strength' implies a certain amount of elasticity. This is the point that MR. Lee makes in his book... best accuracy ( what ever that may be ) "should" be achieved at or close to the 'ultimate compressive strength' of the projectile...
As for the the other ones.. they seem arbitrary and don't seem to make any allowances for alloys... Just my 2 cents

Tensile or compressive strength is usually quantified at the point the material yields in an unconfined environment. The terms/definitions, from elastic deformation to failure, are distinct points of the materials strength during loading with different graphs for each type of loading.

[38-55]

45 2.1,
Please indulge me as I try and try and wrap my little pea brain around this concept....
All the lead 'hardness' testers do just that, they test the hardness of lead in a static unconfined environment. What really is more important to the cast bullet shooter is at what point under what loading the bullet fails... and being a dynamic environment we can't truly measure that except by examining spent bullets and results on target so to speak..
No wonder Mr. Lee recommends ( as a rule of thumb) to start under the ultimate compressive strength of the bullet as derived with his gizmo and , according to him you should get your best results at 10% or so less than maximum compressive strength.. Makes sense since it would seem that there is no way ( other than results based empirical data) to really measure things... What it would seem He is trying to do is get a 'starting ' point based on strength of bullet and chamber pressure to cut down on the trial and error method... Yup, Mr. Lee is definitely a engineer..
Thanks for your indulgence,
Calvin

[45 2.1]

45 2.1, Please indulge me as I try and try and wrap my little pea brain around this concept....
All the lead 'hardness' testers do just that, they test the hardness of lead in a static unconfined environment. And a formula is used to convert that to: 1) An ideal pressure range to use or 2) as Mr. Lee says something about ultimate compressive strength. Lots of assumptions going on there. Only general facts? can be assumed from those simple tests. Alloys can have the same hardness and differ greatly in actual properties. What really is more important to the cast bullet shooter is at what point under what loading the bullet fails... and being a dynamic environment we can't truly measure that except by examining spent bullets and results on target so to speak..
So very true.............................................. ...........................
No wonder Mr. Lee recommends ( as a rule of thumb) to start under the ultimate compressive strength of the bullet as derived with his gizmo and , according to him you should get your best results at 10% or so less than maximum compressive strength.. Makes sense since it would seem that there is no way ( other than results based empirical data) to really measure things... What it would seem He is trying to do is get a 'starting ' point based on strength of bullet and chamber pressure to cut down on the trial and error method...That would be a good place to start, but what is he baseing that ultimate strength on, a formula involving tensile strength as a determineing factor or something else? Yup, Mr. Lee is definitely a engineer.. Engineers usually do not judge a materials properties based on the wrong loading state, that is done by people who don't understand the principles. I would have to see how he determined his approach, but the idea has merit.
Thanks for your indulgence, Calvin

[Bret4207]

[QUOTE=45 2.1;232482] The boolit is not under tension....!! It is under compression, its being pushed up the bore by powder gases. The tensile strength of lead is much, much less than its compressive strength...............

Bob- Wouldn't you consider tensile strength along the same lines as sheer strength and isn't sheer strength a factor to be considered in relation to the alloy withstanding rotational forces applied by the rifling?

[45 2.1]

[quote=Bret4207;232562]

The boolit is not under tension....!! It is under compression, its being pushed up the bore by powder gases. The tensile strength of lead is much, much less than its compressive strength...............

Bob- Wouldn't you consider tensile strength along the same lines as sheer strength and isn't sheer strength a factor to be considered in relation to the alloy withstanding rotational forces applied by the rifling?

Nope........... Shear strength is for a more brittle (not ductile as lead is) material and is tested in compression. Rotational forces would be somewhat inline with the torsional strength of materials.

[Bret4207]

If I'm thinking of this correctly the boolit starts into the leade and is compressed and (hopefully) uniformly distorted by the rifling, forming the reverse image we all love to look at. Where does torsion come into play? Once the boolit starts to follow the rifling there would be no more possibility of torsional stresses would there?

Maybe you could expand on your understanding of the difference between "compressive strength" and "tensile strength" as they relate to the issue at hand. I have no engineering background, but I am a pretty darn good mechanic IMO and would like to understand what you mean.

[Pat I.]

After reading Richard Lee's Second Edition of Modern Reloading, I am somewhat reluctant to continue shooting boolits powered by fast shotgun or pistol powders. He makes some compelling arguments against this practice. At the other end of the spectrum is using a slow powder and reducing it by about 20% and going from there. I've shot cast boolits in handguns for a long time but am relatively new to the cast boolits in rifles. What do you think?

I think the first answer to your question pretty much sums it up.

[45 2.1]

If I'm thinking of this correctly the boolit starts into the leade and is compressed and (hopefully) uniformly distorted by the rifling, forming the reverse image we all love to look at. Where does torsion come into play? The twisting of the boolit while takeing the rifling. Once the boolit starts to follow the rifling there would be no more possibility of torsional stresses would there? Some as the boolit would still try to overtake the rifling. One side of the land engraving is always in firm contact and the other side is not.

Maybe you could expand on your understanding of the difference between "compressive strength" The strength of a material while it is being compressed (squashed so to speak) and "tensile strength" The strength of a material where it is being stretched (pulled apart) Either of the terms in reference to a load per unit area. as they relate to the issue at hand. I have no engineering background, but I am a pretty darn good mechanic IMO and would like to understand what you mean.

[38-55]

45 2.1 Sir,
Here's Mr. Lee's way of going about where to start... Take a sample of the bullet you are going to shoot. File a flat spot on it and compress it with a 5/32 steel ball at 60 pounds for thirty seconds. Use a little pocket microscope to determine the size of the indentation to the nearest thousandths. Use the little table he provides to find the 'strength' of the bullet in psi. Then select
a load that does not exceed the max psi in his little column. Go and find a load that is less than the max but close to it and try it.
For example say you have a 30-30 and lymans 311041 that casts at or about 170 gns. File a bullet and get a 'reading' of .057 which on his chart reads to be bhn 16 or a strength of 22703psi for a max pressure ( chamber) of 20433psi. Go to his load data ( which is conservative in the extreme IMHO ) and say all I have is varget... So I look at the data and come up with 20 grains of varget at 20,000 psi and I use that for my starting point.
I realize this is getting away from what the man asked/stated when he started this thread... But it works for me as a starting point. An aside to all this is that it is nice to have some idea of what to expect from one's alloy before shooting it...
Stay safe
Calvin

[JohnH]

I read this till my eyes went "TILT TILT TILT". I ain't very learned, but it seems quite simple to me, a bullet can be stripped with fast or slow powder, all ya got to do is drive it faster than it can stand to be shoved. How do you prove that? With a chronograph and paper. Just because Mr Lee says his sons rifle performed poorly with such and such a load don't make that a universal truth. I'd have had more respect for Mr Lee's report if he had said he fired the stuff himself, but that's some what beside the point.

I drive the Lee 312-185 out of my M44 at 1700 fps with 2 grains of 4895 and 55 grains of 860 ( a full case) , and get 2" groups. I shoot the same boolit with 9 or 11 grains of Blue Dot at 1100 and 1250 fps respectively and get......2" groups. Could be that my M44 is a 2" rifle, and it don't make a stink bombs difference what powder, boolit, BHN or primer I use. (Trust me, I have experimented too)

I've read all kinds of debate on fast versus slow powders with cast, and what I've come to as my defining point of which I choose is this, What do I want the load to do? For plinking loads that I shoot daily in my back yard, I choose pistol/shotgun powders as they are relatively quite and my neighbors don't complain of my firing 20-40 rounds in the evening after work. If I'm working on a cast boolit load to hunt with, I seek out a powder that will give me 1700-2000 fps with the same or reasonably close accuracy as I get from my daily plinking loads. For those times that I work with full velocity, full pressure jacketed bullets, I go to a range where no one complains of the noise level.

I think that too often debates like "Slow vs Fast" turn into a one is better than the other argument (In this case it's turned into a discussion of algabretic proportions ) when in fact both speeds have something to offer if we look at the whole picture of our shooting needs.

I for one want both speeds available on my bench, as both speeds fill specific needs.

[38-55]

JohnH,
I agree whole heartedly with you. Fast and Slow powders are just tools in your tool box and different powders for different jobs. It really is that simple. But being a caster and a reloader I want to know why things happen and so sometimes I just think/explore things to their logical conclusion ( and sometimes not so logical conclusions).
Calvin