Diminishing Returns?

[Dphar]

Sorry, didn't address your question about how it's determined.

The only way to specifically address your personal rifle is to have it chronographed with different powder charges - mine was measured at 15 ft from the muzzle and the results were plugged into a ballistics calculator to extrapolate the results at various distances.

You don't have to go to that extreme. Often times data collected by others using a similar rifle/barrel will be "close enough" to apply - likewise, sources such as Lyman publish data that will also be close enough to help you determine if using say 100 grains is significantly better than 80 grains (or whatever).

For "me" black powder is expensive ($34/lb including tax) and I have to drive 3 hours, one way, to buy it.

Shooting 80 grains I get about 90 shots per pound. If I move up to 110 grains I only get about 65 shots per pound.

And for shooting all that extra powder I only would get 10% more retained energy = NOT WORTH IT, in my case...

People make a mistake in assuming that at the velocities we run that energy is a good guide for killing power. Its not. Its not really valid for anything but gives the small bore smokeless crowd a reference. For example a 243 will produce a lot more energy than a 45-70 BP load will. But if I have a bear with an attitude at close range the 45-70 is a better choice.
It is difficult to increase the killing power of a RB with velocity. Since BP is velocity limited energy is not a good guide. Ball diameter is the key. Also given a pure lead ball they will usually penetrate similarly in tissue (bone is another matter) since the velocity is the same and their ballistic C is similar though again a large ball with is better density will penetrate a little better. On deer in my expericence a 50-54-67 cal rb all penetrate about the same. However, while the 50 and 54 both kill well they are not in the same class as a ball weighing twice what a 54 ball does.
The reason for higher velocity, say 1800 fps vs 1400 at the muzzle is TRAJECTORY. The 1800 load will shoot FAR flatter than one at 1400.
This is the great advantage of shooting more powder. If shots are taken at less than 50-60 yards a 45 caliber with 45-50 grains of FFF will kill deer well if it shoots OK. So if shooting from a tree stand at pistol ranges lighter charges will work if the accuracy is OK. If the hunter is in the west or someplace where the shots are likely to me 100+ then a load of 65-80 is better since it will shoot flat enough to 100-120 to require no hold over from the point of aim for 40 or 50 yards.

Dan

 

[Claude Mathis]

I'm so "old school", the tightest group is all I care about. I'm not interested in velocity, foot pounds or formulas. I'll leave that to the guys in the laboratory. :wink:

And you would do that even if the most accurate load required more than the "most efficient load" of powder? You are one radical dude.

IMO, the most "efficient" load is the one that hits the mark in the field. I don't care how it measures in the lab. :wink:

 

[azmntman]

:thumbsup:

 

[hanshi]

I go along with Claude on this one. Formulas don't mean #&*% to me. I have a chronograph and can know what I'm shooting. I work up a load that is accurate at the distances I shoot it and mostly stay there. Within reason, I don't worry about velocity and could not care less about energy. My loads take game efficiently and that's all I'm interested in.

Once the point is reached where the returns start to diminish; THAT is the point of diminishing returns and is mostly irrelevant. It may or may not be the best or most accurate load so doesn't really matter in and of itself. If going higher with loads past this point is needed or wanted it certainly makes sense to go for it. Wasted powder is in the eyes of the shooter and is not a given or carved in stone. Some just like heavier loads and some don't and that's is perfectly okay. Our ancestors were primarily in the Dump Powder Prime & Load club. Is there anyone here that has documented (HC/PC) proof that shows Davey Crockett used an x + y = Q x 9.68 + 1 formula? Talk about tempest in a tea pot!

 

[Zonie]

Well, of course ole' Davey Crockett wouldn't have used a formula like that!

He had to retake his first grade addin' & subtractin' course 3 years runnin before his teacher would promote him to the second grade addin' & subtractin' class!

Now, ole' Danial Boone on the other hand.........


:rotf:

 

[tenngun]

Just reading this got me thinking so I'm just toss this out to heer some opinions on it.
First I have to say dead is dead. For me I have found charges of 65-80 grains good killers dependind on my gun. Second you need to believe in your gun. If you think you need a magnum load it dont hurt to shoot it. better to much then too little
But looking at this formula just set me a wondering what effect the extra wt of powder would have. A minie gets more energy from a given powder charge then a PRB since there is less inertia to over come,so pressures behind the ball decrease faster. For a time inside the barrle powder and ball look like a rocket and increased powder weight slows the accceleration,only to increase the accelration later as more powder is consmmed and pressures dont decrease as fast. Then the extra time that a ball is exposed to pressure in a longer barrel would mean would mean a more effecent use of the powder.
Ultimently do you think a formula that works for a 28 inch barrle is applicable to a 36 42 or44 inch barrel.And since you increas the diameter of a circle by a factor of 4 every time you double the diamete do you thnk a formula that works on a .45 would work for a .58?

 

[zimmerstutzen]

Ol' Davey and Dan'l never designed a remarkably accurate firearm. They lived at times when powder and lead were at a great premium and were not wasted on frivolities. Their reputations as hunters and marksmen were largely through sensational tall tails and the era equivalent of penny dreadfuls. Fact is, they most likely used less in their average charges than the Davenport formula would have calculated. Ol Dan'l hunted the eastern woodlands where short range shots were the rule.

Increasing powder for hunting wide open spaces is of marginal utility for the mere reason that sonic round balls decelerate faster down range than sub sonic balls. 50 percent more powder rarely nets more than 20 extra yards anyway. Flatter trajectory is largely a myth. The round ball fired over the "Dave3nport" charge is not all that greater than a dangerous increase in powder charge at 100 yes.

As explained above, it is a starting point for finding an ideal charge. Stupid people ignore conventional wisdom and spend unnecessary hours trying to arrive at the magic charge by starting at 5 grains and working their way up to 120 grains in their long rifles. Re-invention of the wheel is a fruitless exercise. We build on what those before us have discovered.

Formulas help us understand the ballistics of hitting the target. Frankly, I personally don't give a rat's fart about hunting loads. I aim for shooting MOA as closely as possible as repetitively as possible to compete on paper. Near any greenhorn can shoot MOD at 50 yards offhand. Primitive beings reason that airplanes fly inspite of gravity not realizing that they fly because of gravity. Same for shooting. There are those who are happy when "gun go boom" and those happy when they shoot a 1 inch 5 shot group at 100 meters. It doesn't take an understanding of gravity, ballistic coefficients, etc to shoot a tight group, but it just might help.

All Davey and Dan'l BS is just that. How much historical evidence exists that shows they were such superb marksmen, other than tall tails? Do we have targets, scores, match results? Did they compete anywhere against real marksmen of the day, or were they merely reputed to be the best of a motley collection of back water shooters?

I suppose the Wright Brother's did not have to know anything about gravity, air pressure, etch to design a working airplane. Does anyone realize how different the world would be, had the world distributed direct current as Edison wanted instead of alternating current? Much less why it is easier to transmit alternating current? Any fool can run an electric wire from one contact to another. It takes an understanding of electricity to figure how heavy a wire is required for a particular distance and voltage. That understanding may not change the end result, but it beats trying to run 240 volt 50 amps on a 30 gauge wire and finding it doesn't work and then trying a lighter wire. The same is true for shooting. No reason to waste hours and powder testing loads that do not match the rifling and barrel length.

 

[galamb]

I think this, like many formula's are looked it from the wrong direction.

This isn't saying "use this" and everything will be better/stronger/faster - but that's what many want to hear - just take this pill and everything is good.

However it was ultimately figured, it was only meant to determine how much powder can be consumed fully in a given barrel length with a given caliber.

No "magic bullet", just a single piece of information.

I have never read in any of the hundreds of posts that tossed this (theory, formula - pick a term) around that using this was a max load or using more or less powder "wouldn't work".

Much like the Greenhill formula on rifling twist, every time it is brought up there is a whole bandwagon that have all kinds of anecdotal "proof" that it's "hoooey". Again, another formula that was never purported to be "the only way" or if you don't use it your results will be disastrous.

But you don't have to be a scientist to realize that a given amount of black powder will eventually consume itself in a given amount of space and time - maybe it's 11.5 grains per cubic inch and maybe it's not but nobody has stepped up with lab tests to "disprove" it.

An if it is correct or close, then a given caliber of a given length will consume a given quantity of powder before/at the instant the ball OR bullet exits the muzzle.

As far as I can see, that's all the formula was attempting to determine.

So if you want to "get close" to burning all the powder you poured down the muzzle, which would be near 100% efficient, then use the formula.

If you don't care or your goal is greater velocity, down range energy or whatever, then ignore it.

But if I was building a rifle for a very specific set of circumstances with specific performance expectations I certainly would first (develop) a "virtual barrel" using every formula I could find before I would fill out the barrel order form.

Might be "hoooey" but maybe just a little more scientific than going with "what some guy shoots".

 

[zimmerstutzen]

Tenngun, the Davenport formula skews off for barrels under 40 and over 54. As caliber increases, the powder column gets shorter and the burning powder is not be used pushing the weight of powder ahead of it.

Just as the Greenhill formula for matching bullet length to twist needs to be adjusted for bullet speed, so to Mr. Davenport apparently never got around to the adjustment needed for small and large calibers.

Personally, I think the thought that there is one, or just two magic combinations of powder patch and ball for accuracy is BS. Yes there are many inaccurate combinations, but I think there is a range of accurate load for the barrel length and rifling configuration.

I have won matches with very small loads, such as 30 grains in a 54 caliber Hawken style, where the point of diminishing returns was probably 80 grains. Whether I can hit a deer at 120 yards on a first clean shot is totally irrelevant to whether I can hit a dime sized spot twenty or thirty times in an afternoon. I was never a great shot. But I can win because I am a more consistent loader, more consistent with hold and follow through and able to reload, hold and shoot 80 times in an afternoon. Harry Pope realized that shooter fatigue at a match was a large factor in destroying accuracy and he designed his guns to load in a way that reduced handling and fatigue.

 

[tenngun]

I'm sorry sir I did not mean you post was "hoeey".Or for that matter any one else on this forum. All in all for most shootes it seams the sweet spot for them hovvers around the same spot. I have noticed most rules however break down outside of a narrow range. Take the 1 grain per caliber rule.35 grains is a good load for a .36 and 45 will do well in a 45.50 grains may be a bit light and 58 might be real light although I do shoot 65 grains with 7/8 oz in my 62.
I remeber a cook that was on tv who could mesure a teaspoon or tablespoon in his hand and increments very close,covering a prb with powder in your hand will give close to 1/3 wt of ball in .40-.54 size another "good" rule that starts to fail as soon as you go to big or little. With ML running from .32-10 gage most of our math formulas miss the one size fits all boat. Every shooter needs to spend time playing with his gun to find his sweet spot.
I would never discount your experince or your method and sorry if I gave that impression. :redface:

 

[galamb]

Sorry if I gave the impression that I though "you" called it "hooey" :grin:

I was just making a broad/general statement to no one in particular.

I have enjoyed this post (ok, maybe I like to argue a point a bit too much, but it's entertaining).

And I do appreciate differing points of view, experiences etc.

If we never have out thoughts/beliefs challenged, we will never learn anything new or fully understand what it is that we in fact, believe.

 

[hunts4deer]

The Davenport formula isn't supposed to give you the fastest load, the maximum load, the most accurate load, the most economical load, the starting load, the ideal load, or any other "recommended" load.

It is just a general formula that supposedly would approximate the number of grains, beyond which, the additional gain in velocity per grain added starts dropping off. In other words, if every additional 10 grains of powder had been increasing velocity by 50 ft/sec, past this theoretical point, the additional 10 grains start adding only 40 ft/sec, then 30, etc. I suspect that the 11.5 was an empirical number developed by average observed increases, but in fact would be a different number for every caliber. The calculated load amount it gives is way above anything you would really use anyway (145 grains for a .62 cal).

I just find it humorous that every time these kinds of theoretical questions get asked, there are an awful lot of people responding as though you has insulted their mother. Why the hostility? :cursing: Its a fun discussion. :hmm:

 

[Claude Mathis]

I just find it humorous that every time these kinds of theoretical questions get asked, there are an awful lot of people responding as though you has insulted their mother. Why the hostility?

My guess would be, the juxtaposition between 18th century tradition and the 21st century laboratory? :wink:

 

[galamb]

I found this discussion nice and civil.

The points were well argued and it didn't degrade into name calling or personal attacks which is somewhat rare in a longer back/forth discussion with diametrically opposed views.

None of us probably changed our minds one way or the other, but at some later point anyone who stumbles over this post will have the benefit of reading the opinions/information well discussed by both "camps".

 

[Chris Nolin]

Agreed. As the OP, I feel like I got my answer and more! Thanks all!

 

[longcruise]

I'll see if I can quantify some of the responses you have got here.

This is some data from my 45 cal shooting between 70 and 110 grains of FFF in 10 grain increments.

(the data was ran to figure point blank range with escalating charges and not specifically for "diminishing returns" but the results are what they are - in this instance I will compare the speed and foot pounds of retained energy at 100 yards - a good "max" range with a 45 cal)

Grains - speed @ 100yds in FPS - FtLbs @ 100

70 grns - 908 fps - 250 ft/lbs
80 grns - 949 fps - 274 ft/lbs (14% more powder = 10% more "thump")
90 grns - 973 fps - 287 ft/lbs (12.5% more powder = 2.5% more "thump")
100 grns - 985 fps - 295 ft/lbs (11% more powder = 2.8% more "thump")
110 grns - 1007 fps - 308 ft/lbs (10% more powder = 4.4% more "thump")

I can't believe that these numbers drew so little comment as to their veracity! If indeed you have gotten similar results with other rifles with this chronograph, then your chrono is absolutely out of whack! :shocked2:

Here are some velocity results from a TC .45;

Shot on 05/30/10 with TC .45, goex 3f, wally duck patch, spit lube

50 grains
1517

70 grains
1680 +163

90 grains
1865 +185

120 grains
2031 +166

I know, we often explain these differences with powder differences, patch differences, lube differences, barrel length, etc., etc. but I assure you in the case of your numbers, your chrono is bananas.

 

[George]

I know, we often explain these differences with powder differences, patch differences, lube differences, barrel length, etc., etc. but I assure you in the case of your numbers, your chrono is bananas.

Look closer, you'll see that he said "in this instance I will compare the speed and foot pounds of retained energy at 100 yards ", and "Grains - speed @ 100yds in FPS - FtLbs @ 100", not muzzle velocity.

Spence

 

[galamb]

Yes, that is my 100 yard numbers extrapolated from measurements taken 15 feet from the muzzle.

The muzzle velocity rose from 1530'ish FPS to 1960'ish FPS at the muzzle over the range of powder weights that I shot.

But numbers at the muzzle are of little comparative value when you are talking about shooting a critter at the "edge" of your effective range - which happens to be the only reason you would significantly up your powder charge anyhow in my opinion.

The only way I get velocities above 2000 fps at 100 yards is if I'm shooting my 30-06 :idunno:

 

[longcruise]

Ol' Davey and Dan'l never designed a remarkably accurate firearm. They lived at times when powder and lead were at a great premium and were not wasted on frivolities

Actually, the pre rev frontiersman "wasted" quite a lot of powder and ball on these "frivolities". It was a primary form of entertainment and a vehicle for the establishment of an individuals prestige among other hunters. Most social get togethers included a shooting contest.

How well did dan and davey actually shoot? Who knows, but there is documentation of the typical backwoodsmans shooting ability in accounts of the frontiersman who reported in large numbers when called upon to fight in the revolution. As they gathered companys and marched to the east they put on many a shooting demonstrations along the way. Some of their shooting was quite astounding!

Increasing powder for hunting wide open spaces is of marginal utility for the mere reason that sonic round balls decelerate faster down range than sub sonic balls. 50 percent more powder rarely nets more than 20 extra yards anyway. Flatter trajectory is largely a myth.

It's not about the deceleration so much as it is about the velocity within the arc of trajectory. You are correct of course in that the faster a ball starts off, the more rapid is the deceleration. The difference in velocity at 100 yards between a .495 ball starting at 1200 and 2000 fps respectively is only 200 fps. However, the 1200 fps ball gives an 8" PBR out to 115 yards whereas the 2000 fps ball gives an 8" PBR out to 145 yards. An additional 30 yards of range is a lot with an ml gun and does make a big difference in the "wide open spaces". At 145 yards these balls give 741 and 900 fps respectively. Both adequate to kill deer size game but the 1200 fps ball has a PBR of 15"!

 

[Billnpatti]

Understandable.