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Physics help needed on ballistics question

Discussion in 'Shooting Related Threads' started by joe kuhn, May 11, 2013.

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  1. joe kuhn

    joe kuhn Furry Lives Matter TS Supporters

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    Need help. I've got this chart from an old Remington site that shows #6 steel having the same pellet energy as #7-1/2 in lead.


    [​IMG]


    My friend Jay found a Randy Wakeman article that says the chart is not accurate for the lead statistics. See link above. Randy says the lead statistics are over rated (see his ballistics myth) and the steel stats are under rated (first part of article). If he's right this would put steel at an advantage over lead which doesn't seem plausible, but hey. We need to be accurate. Here is my question.

    Can we learn something about lead versus steel and their energy in breaking targets by just looking at them informally. My proposal is to weigh 100 pellets of #6 steel and 100 pellets of #7-1/2 lead. If they are close, doesn't that indicate they would break targets in a similar fashion if they started out at the same speed?

    I guess it's a force question. If we rolled a pellet of each over the edge of a table, would they hit the floor with the same force? I know steel is lighter than lead when you consider the same volume, but in this case, the steel pellet is larger, so it seems to me it would hit the floor with approximately the same force.

    Some other details: the shot cup on a steel wad is longer than the shot cup on a lead wad. And you should see how steel #6s smoke bios at 16 yards. They are a 'secret' favorite for yardage shooters at our club which requires steel shot.

    Joe
     
  2. wayneo

    wayneo Active Member

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    Joe, this is from Outdoor Life. To answer your question, yes, energy shoube be the same or close. E= M(v^2). The simple version.


    Shot Physics 101


    The ballistics answer to the steel-shot problem is founded in physics and the laws of motion. Everyone remembers the fundamentals from high school. When applied to shot pellets it goes like this: If you have two spheres of equal diameter but of different weights, and set them in motion at equal velocity, the heavier sphere will retain its velocity (call it energy if you want) better than the lighter sphere. And there you have the fundamental difference between lead and steel shot.

    So let's make some real ballistics comparisons between lead, which has a specific gravity (S.G.) of 11.35 and iron (steel is an alloy of iron), which has an S.G. of 7.89. The higher the specific gravity, of course, the heavier the metal. For example, gold has an S.G. of 19.32 and would make a wonderful shot.

    Let's say that we fire No. 4 lead and steel-shot pellets at a muzzle velocity of 1,300 feet per second (fps). At 40 yards the lead pellet would have a remaining velocity of 747 fps and energy of 4 foot-pound (ft.-lb.). The steel shot, however, would have a remaining velocity of 627 fps and energy of 2 ft.-lb. at 40 yards-only half as much as the lead pellet. Thus, in order to make steel shot as effective as lead we have to either fire it at a higher velocity or use bigger -heavier-steel shot. Let's suppose we fire the steel shot at 1,500 fps, which yields a 40-yard velocity of 679 fps and increases energy to 2.34 ft.-lb. This obviously isn't a great improvement, so next we try larger No. 2 steel shot fired at 1,300 fps. The 40-yard velocity is now 678 fps and energy is 3.59 ft.-lb., which is getting closer to that of lead. Finally we up the velocity of the No. 2 steel shot to 1,500 fps and what we get at 40 yards is a remaining velocity of 737 fps and energy of 4.29 ft.-lb., which is virtually identical to the figures for lead shot.

    Wayne
     
  3. joe kuhn

    joe kuhn Furry Lives Matter TS Supporters

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    Hm, they say larger and faster. I only want larger. Faster is not an option because I don't want more recoil - loads are both 1 oz. If the physics of recoil tells me this, why doesn't it work the other way - out the end of the bbl? Something doesn't jive.
     
  4. spitter

    spitter Well-Known Member TS Supporters

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    May I interject a question... I am, by my own admission, not well informed on this subject of physics... but WayneO's numbers cause me to ask... so please indulge me.

    If based upon WayneO's comments that #2 Steel thrown at 1500fps is somewhat comparable to #4 lead thrown at 1300fps... "... we up the velocity of the No. 2 steel shot to 1,500 fps and what we get at 40 yards is a remaining velocity of 737 fps and energy of 4.29 ft.-lb., which is virtually identical to the figures for lead shot...."

    Look at the chart above that we've been using for the past number of lead v. steel discussions... Joe has also posted the link from Randy Wakeman's article, which suggests that the present data, used by the industry, is incorrect.

    However, Wakeman further suggests that lead performance is overrated and that steel shot is underrated...

    If WayneO's numbers are accurate, I think it confirms Wakeman's premise about the charts, BUT at the same time, in my observation, does it not place steel in an even more poor position against lead... Am I interpreting what I am seeing correctly?

    Thanks in advance,

    Jay
     
  5. BigM-Perazzi

    BigM-Perazzi Well-Known Member

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    You certainly have Neils contact info.

    Certainly available with data points and graphs. Lol
     
  6. Neil Winston

    Neil Winston Well-Known Member

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    Joe, what doesn't jibe is the way all of what you have quoted leaves out the effect of the size of the steel pellets has on their air drag and so their downrange retained velocity. Randy is talking about hunting and so did not well cover the question you are asking.

    First, a #6 steel pellet is a little (10%) heavier than a 7 1/2 lead pellet, since there are 347 lead pellets in a one-ounce load of lead, and only 315 pellets in a one-ounce load of steel, according the program Ed Lowry distilled all this into, "Shotshell Ballistic for Windows."

    Here is the comparison that program produces:

    #7 1/2 lead, 347 unbuffered pellets, one-ounce loads, launched at 1235 fps (3-foot reading)

    30 yards: 737 feet per second retained velocity, 1.52 foot-pounds retained energy

    40 yards: 633 feet per second retained velocity, 1.12 foot-pounds retained energy

    #6 steel, 315 unbuffered pellets, one-ounce loads, launched at 1230 fps (3-foot reading)

    30 yards: 677 feet per second retained velocity, 1.41 foot-pounds retained energy

    40 yards: 567 feet per second retained velocity, 0.99 foot-pounds retained energy

    But you need some perspective to see what all this means, so let's look at something you well know, #7 steel shot.

    #7 steel, 420 unbuffered pellets, one-ounce loads, launched at 1230 fps (3-foot reading)

    30 yards: 643 feet per second retained velocity, 0.96 foot-pounds retained energy

    40 yards: 532 feet per second retained velocity, 0.65 foot-pounds retained energy

    That very last figure, 0.65 foot-pounds of energy, is often quoted (by Tim Woodhouse, as I remember) as the minimum required to break a clay target. This is certainly nonsense when presented, as it is, as a single number. What you would need is what toxicology calls "LD50" (lethal dose 50), that is the dose required to kill half the tested things.

    The number that would be a required would be something like LD90 (break 90% of the targets) or LD95 or whatever you are satisfied with. My guess is that the energy needed would grow to very high very fast if you got much over about LD90 or LD95. In any case, it's not a single number; you and your club members are the best judges of whether 0.96 foot pounds of energy (your steel 7's) is enough (and from what I have read here is certainly is) and as you test farther back you could probably make very accurate estimates as what begins to be "not enough." You would need the data to be from your best shooters and careful and complete notes.

    One problem you have not thought about enough (in my opinion) in your drive to get #6 steel approved is pellet count. The change to steel 6's is like a drop to 7/8 ounce of lead 7 1/2's and is that a good thing to shoot at handicap? I don't know, but I wouldn't do it is there was another way to get the targets broken - though there may not be.

    Yours in Sport,

    Neil
     
  7. bevolt

    bevolt Member

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    Joe,

    If you look at the tables in Randy's article both the steel and the lead energy at 40 yds is too high in the old ballistics table. For example, #4 steel at 1365 fps has 2.5 ft-lbs of energy at 40 yds in the old table, but in the newer table published by Ed Lowry, #4 steel at 1500 fps has 2.48 ft-lbs at 40 yds.
     
  8. wolfram

    wolfram Well-Known Member

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    Because the steel is lower density you need to use a larger diameter pellet to get the same mass as a lead pellet of a given size. But when the pellet diameter increase so does the suface area that are exposed to friction with the air. So the larger diameter steel pellet looses velocity (and energy) more rapidly than the smaller diameter lead pellet of the same mass.

    This is why waterfowlers use both larger shot size and higher initial vleocity such that they approximate the performance of their old favority duck loads of years past. (no steel aint as good for hunting ammo)

    So the trick is use the largest steel pellet in as big of a payload as possible (allowable) and shoot it at the highest velocity possible (practical). Pretty tall order to duplicate the performance of a 1 1/8 Oz lead target load with #71/2 @ 1,200 Fps using steel shot and the guys out there shooting steel target loads know this all too well.
     
  9. joe kuhn

    joe kuhn Furry Lives Matter TS Supporters

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    I like Neil's point about loosing pellet count with 1 oz of #6 steel because I think it might be a real issue.

    As we move from singles league to yardage shooting at our club I will look at this. I will tell you 1 oz of #6 steel absolutely smokes bio targets from 16 yards. For yardage, I have an answer if pellet count is a problem - go up to 1-1/8 oz of steel #6.

    Since 1 oz of lead #7-1/2 has 347 pellets, I figured I'd weigh 347 #6 steel pellets and see how close it is to 1-1/8 oz. Back in a few...
     
  10. Neil Winston

    Neil Winston Well-Known Member

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    Maybe 315 x 9/8 = number of #6 steel pellets in 1 1/8 ounces?

    Neil
     
  11. zzt

    zzt Well-Known Member

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    Joe, you said you didn't want any more recoil, so why go to 1 1/8 oz. Stay with 1oz #7. It has enough retained energy.

    I watched a friend of mine run out of trap loads at 27 yard handicap practice. All he had left were 7/8oz #9 @ 1200fps skeet loads. He used them and ran the last 25. No little chips, mostly smoke. I was astounded. Retained energy @ 40 yards was .5 ft/lb, so you are still ahead of that at .65 ft/lb with steel #7.
     
  12. joe kuhn

    joe kuhn Furry Lives Matter TS Supporters

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    zzt, I know, it's a compromise. But maybe 1 oz will do the job. You think so and so do I, but I'll be paying a little more attention to my yardage shooting this year - with steel.

    Above website shows 354 pellets in 1-1/8 oz of steel #6.

    And Randy states, "the superior sphericity of steel shot and resultant better form factor was also ignored." Randy claims steel shot is rounder and flies better and that's all his says. Where'd he get his information?
     
  13. drgondog

    drgondog Member

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    The velocity changes over time and the steel shot loses velocity faster because the larger diameter pellet has more drag...and therefore retains less energy at say, 40 yards, if the velocity of the steel drops below the lead.

    Conversely if the steel 6 has the same mass as the lead 7 1/2 and has a higher Muzzle Velocity, then the Steel 6 initially starts with more kinetic energy..

    If you differentiate the Velocity change with respect to time d/dt(MV), the drop in velocity for steel shot (due to the drag force) is higher per second and somewhere over the 40 yard range the velocities are 'equal' only at that point, and given the mass of steel = mass of Lead shot in this example, the KE is the same AT THAT Point ONLY.
     
  14. joe kuhn

    joe kuhn Furry Lives Matter TS Supporters

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    Looking at Neil's numbers from the Lowry software, the ATA should allow steel #6 for clubs that shoot steel only.

    I originally thought #6 steel and #7-1/2 lead were equal in terms of energy. It turns out, with the newest information, that isn't quite true. Steel is still a disadvantage at size #6 compared to #7-1/2 with lead. That makes the argument for allowing #6 steel at ATA events even more compelling.

    The Lowry numbers bare repeating:

    #7 1/2 lead, 347 unbuffered pellets, one-ounce loads, launched at 1235 fps (3-foot reading)

    _____30 yards: 737 feet per second retained velocity, 1.52 foot-pounds retained energy

    _____40 yards: 633 feet per second retained velocity, 1.12 foot-pounds retained energy

    #6 steel, 315 unbuffered pellets, one-ounce loads, launched at 1230 fps (3-foot reading)

    _____30 yards: 677 feet per second retained velocity, 1.41 foot-pounds retained energy

    _____40 yards: 567 feet per second retained velocity, 0.99 foot-pounds retained energy
     
  15. joe kuhn

    joe kuhn Furry Lives Matter TS Supporters

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    Neil - I'd be really curious to see the numbers for #5 steel. Not that I'd go that far, but just to take it beyond the limit.
     
  16. trw

    trw Member

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    Its interesting to me that none ever seem to recognize the magic number, 350. It is the number of pellets needed at the minimum to get the job done, effectively. Hahaha, but its not really all that facetious when you think about it.

    Add a minimum pellet energy factor & you probably have a truly workable formulae.
     
  17. cnsane

    cnsane Member

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    (with a smile)

    Dammit,,my magic must be broken. I'm at a loss to explain how 7/8ths oz of #7 1/2 ends up running them from the back fence more times than I remember even though I don't have the minimum to get the job done effectivly. I guess it's a good thing I don't rely on magic when I shoot.
     
  18. Setterman

    Setterman Well-Known Member

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    wow, running them from the 27 with 7/8 oz more times than you remember. Please give us your ATA # so we can see your handicap average.
     
  19. joe kuhn

    joe kuhn Furry Lives Matter TS Supporters

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    Magic number list:

    1. 0.65 foot-pounds of energy

    2. 350 pellets

    I'm not being critical, I'm being studious, in case there are issues at yardage with steel, I'd like to be prepared with some kind of explanation.

    Where did the number 350 come from?

    Nearly all our steel shooters use #7. When a few of us have picked up some factory loads with steel #6, 1 oz., 1325 fps, we have hushed up the results because we thought we saw an advantage. Of course, there is an advantage, but it's confusing. If #6 pellets bring more breaking power per pellet, then why does the lesser pellet count not take that advantage away and leave us even with the shooters shooting the same fps, 1 oz #7s? This is at a yardage game called 'the dove'.

    Personally, I've never done very well at the dove which is shot at 27 yards and greater at our steel only club. Most of the shots in this game are from the 27 yard line on trap 2. On neighboring traps 1 and 3 we shoot targets thrown from trap 2 even though we are standing on trap 1, post 1 and on trap 3, post 5. One summer I made it a point to try to improve my dove scores and by coincidence found some 1 oz 6 shot steel loads on sale. With these shells I was finally in the winners circle, or maybe it was runner up. Another shooter and I shared these shells and we did quite well.

    I apologize to Neil for switching topics here back to the ATA rule for shooting #7 steel as a max. I didn't intend to switch back to that topic and start this thread as a way to get the information I needed via a different theme. It just worked out that way. I'm still curious about #5 steel stats.

    Later
     
  20. drgondog

    drgondog Member

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    @ Joe. IF #6 steel ever has more breaking power than 7 1/2 at trap distances it won't be for reasons of Kinetic energy as discussed here.

    A possible explnation is that the greater diameter may be just enough to break a chip from time to time when the 7 1/2 brings dust. perhaps like a 230 gr 45 acp kills better than the much faster 9mm, although that is a wound cavity thingy.
     
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