Do you think the Miller Stability formula that is on the JBM site is accurate for muzzle loader conical bullets?I have been playing with it some and using some bullet weight&length velocity etc.of known accuracy as posted on some forums and those combos do not show as being that good when using the calulater.
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Stability Calculations
- Thread starter Shifty
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Might well point out the futility of the program outside of the few examples used to develop it, as well as the actual measurement techniques used to determine "stability" or lack thereof. Formulas are great somnolents to cover fuzzy thinking by quasi-mathematicians.
Traditional ml are crap. Black powder is crap. Prb is the worst projectile there is and minis just s little better. From 1300 till 1860 improvements were slow and not all that many. The scientific advances made for better ways of understanding bullet flight, but even before this gun designers were groping in the right direction. By 1880 gun makers had outstripped 5 centuries of development. 20 year later beyond doubled the 20 years before.
Formulas of all sorts work on modrrn guns great. All the problems with ml were known centuries ago. They went after a cure with big bores, long sighting radis and getting close. We get kills with low energy fat round balls, we get good groups by working with the limitations. But it's still on a par with square sails snake oil fireplaces.
Formulas of all sorts work on modrrn guns great. All the problems with ml were known centuries ago. They went after a cure with big bores, long sighting radis and getting close. We get kills with low energy fat round balls, we get good groups by working with the limitations. But it's still on a par with square sails snake oil fireplaces.
galamb
58 Cal.
I wouldn't totally toss Miller in the junk heap or even Greenhill (or the modified Greenhill) which Miller based his formula on.
For ML's it does serve a basic purpose, at least for me.
If I decided that I wanted to build a fast twist 40 cal that could shoot bullets "X" long the formula would give me an idea of "what twist" I should have the barrel cut.
Is it 100%, no, but it is moderately better than 1) a guess or 2) the opinion of "some guy" on the internet.
Even in modern CF rounds I find the stability calculations mediocre at best. Now they have it down to stability "factors" and despite having the formula tell me it's "uber-stable" I get keyholes - and other that are "marginal" fly perfectly.
The problem with any formula is that it can never be used in isolation, yet that is continually how we try to use it.
The twist is but one variable - what about your rifling depth and shape, the length of your barrel, powder charge etc etc etc.
Trying to base whether Rifle A, based "solely" on the twist, can fire Bullet B "stable" is an exercise in disappointment...
For ML's it does serve a basic purpose, at least for me.
If I decided that I wanted to build a fast twist 40 cal that could shoot bullets "X" long the formula would give me an idea of "what twist" I should have the barrel cut.
Is it 100%, no, but it is moderately better than 1) a guess or 2) the opinion of "some guy" on the internet.
Even in modern CF rounds I find the stability calculations mediocre at best. Now they have it down to stability "factors" and despite having the formula tell me it's "uber-stable" I get keyholes - and other that are "marginal" fly perfectly.
The problem with any formula is that it can never be used in isolation, yet that is continually how we try to use it.
The twist is but one variable - what about your rifling depth and shape, the length of your barrel, powder charge etc etc etc.
Trying to base whether Rifle A, based "solely" on the twist, can fire Bullet B "stable" is an exercise in disappointment...
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My .40 was based upon a 300 grainer more or less, same twist as many of the mid/late 19th century target shooters used.
In retrospection I'd go a little lighter, little slower twist, just to make things easier. Have found that I prefer about 240 grains.
The Greenhill and other calculators give me pretty much the same figures.
In retrospection I'd go a little lighter, little slower twist, just to make things easier. Have found that I prefer about 240 grains.
The Greenhill and other calculators give me pretty much the same figures.
I have had excellent results for my .72-caliber rifles 1:72 twist. I have a built-to-order 775-grain conical whose accuracy/consistency is clover leaves at 25 and 50 yards, "in the black" at 85 yards - the farthest I have shot with any of the 72s. The accuracy testing occurred from a bench, rifle being supported by my elbows, The consistency is that this accuracy is maintained from 110 grains to 150 grains Goex FFg and CCI #11 Magnum caps. Surprisingly, points of impact varied less than four inches among the several different amounts of FFg I tried.
When using the stability calculator, temperature and altitude (pressure in the calculator) are important. Use them truthfully.
I also have drawings, by Steve Brooks and me, made for my cape buffalo hunt - were some now-unknown benefactor to make it doable. That bullet is 985 grains. Until that benefactor does what a benefactor is supposed to do, the bullet mold will remain our drawings.
Since your query pertains to accuracy potential and stability, there is no need to delve into 775-grains bullets' effectiveness.
FYI: I could not tolerate recoil at 150 grains, so I backed off 10 grains at a time, over several sessions, until I reached 110 grains. Since point of aim and point of impact with Brockman's steel windage & elevation adjustable wing-protected aperture sights were used, 85 yards is pretty much my practical limit, not necessarily the rifles'.
Hope this helps.
When using the stability calculator, temperature and altitude (pressure in the calculator) are important. Use them truthfully.
I also have drawings, by Steve Brooks and me, made for my cape buffalo hunt - were some now-unknown benefactor to make it doable. That bullet is 985 grains. Until that benefactor does what a benefactor is supposed to do, the bullet mold will remain our drawings.
Since your query pertains to accuracy potential and stability, there is no need to delve into 775-grains bullets' effectiveness.
FYI: I could not tolerate recoil at 150 grains, so I backed off 10 grains at a time, over several sessions, until I reached 110 grains. Since point of aim and point of impact with Brockman's steel windage & elevation adjustable wing-protected aperture sights were used, 85 yards is pretty much my practical limit, not necessarily the rifles'.
Hope this helps.
I've never been to South Africa, based on photos and movies in my minds eye I see country that looks like east New Mexico. Warmer however. How close can you get to Cape buffalo? I would think that .72 would be up to elephant. Do you ever hunt with ball?
Interesting post. I once had an original CW rifled musket in .72 cal. It had 12 round lands and grooves. Speculation, and some research, indicated it was one of 2,000 of an experimental lot from Austria. It had a Nock style breech that needed 120 gr. FFg bp to fill. Using a prb the recoil was substantial. Painful off the bench. But it was accurate. Regretfully, I sold it. 
Would have made a good, and interesting, hunter. Never did find a minie/conical mould for it. The extra projectile weight would have made it a really punishing kicker.
Would have made a good, and interesting, hunter. Never did find a minie/conical mould for it. The extra projectile weight would have made it a really punishing kicker.
Could you drop the charge a bit and use a filler to fill your chamber?
While I have never hunted with RBs, Gene Gordner will complete the first of a matched pair of English-style 72s sometime this spring. I have purchased a Lyman .715-inch RB mold and intend to work with Gene to determine whether the rifle and I can be efficient. If we can, I suspect I will change to RBs solely because recoil will be substantially lower while "killing/stopping" ability should not deteriorate on elk and deer.
At my age with my health "killing/stopping" is extremely important. In western Montana where I hunt, terrain is fiercely vertical. An animal running several hundred yards before dying would create a nightmarish job of getting it to the truck - regardless whether is it quartered or filleted or [fill in the blank]. Since single shot muzzleloaders will allow one shot, no pressure or speed needed for finishing shots, it must be the most potent I can deliver - hence 72s. Performance of 775-grain conicals is breathtaking through-and-through with massive destruction I have never seen from any other bullet, centerfire or muzzleloader.
***
I have no desire to hunt any African animal other than cape buffalo. If my benefactor delivers, I would love to have a walking hunt. For me, the hunt is more important than a shot. I fantasize a mid-Victorian hunt à la William Cotton Oswell.
Hope this response is helpful.
At my age with my health "killing/stopping" is extremely important. In western Montana where I hunt, terrain is fiercely vertical. An animal running several hundred yards before dying would create a nightmarish job of getting it to the truck - regardless whether is it quartered or filleted or [fill in the blank]. Since single shot muzzleloaders will allow one shot, no pressure or speed needed for finishing shots, it must be the most potent I can deliver - hence 72s. Performance of 775-grain conicals is breathtaking through-and-through with massive destruction I have never seen from any other bullet, centerfire or muzzleloader.
***
I have no desire to hunt any African animal other than cape buffalo. If my benefactor delivers, I would love to have a walking hunt. For me, the hunt is more important than a shot. I fantasize a mid-Victorian hunt à la William Cotton Oswell.
Hope this response is helpful.
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Rifleman1776 said:Interesting post. I once had an original CW rifled musket in .72 cal. It had 12 round lands and grooves. Speculation, and some research, indicated it was one of 2,000 of an experimental lot from Austria. It had a Nock style breech that needed 120 gr. FFg bp to fill. Using a prb the recoil was substantial. Painful off the bench. But it was accurate. Regretfully, I sold it.
Do you recall the particulars as far as what the useful range of engagement may have been?
