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    #31
    Originally posted by enewman View Post
    Yes you are correct with your numbers. A lot of people think when you tell them I'm shooting a 600 gn arrow they think man you got lots of kinetic. But in all reality kinetic very seldom changes more then just a little from where you would have been say at 350 gn arrow. But momentum is what gains.

    I shot some arrows a while back. Shot a 318 gn it was 74 ke. 429 gn 78 ke. 554 gn 79 ke 603 gn 80 ke 694 gn 81 ke. So as you can see ke did not change much. But the 318 gn was .457 momentum the 694 gn was. .711. Now that is a gain.

    So to your question. No. Not shooting same bow at same poundage.

    Once you get your set up. What ever that ke is will be roughly the same unless you can speed up that arrow. That's more poundage
    KE didn't increase in a linear fashion because velocity is squared in the formula. Logic (and basic physics) dictate that a increase in projectile weight will be accompanied by a proportional decrease in velocity all other things being constant(which they are I assume). You can't compare the two, the math is simply too different. I agree with what you are saying in principal but there is no mystery to the equation, it's basic math.

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      #32
      Pure and simple, give me a high to extremely high FOC and MOMENTUM over KE any day of the week!

      More accurate, more forgiving and a lot quieter bow. And if you want to talk drop at extremely long distances, give me the above!

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        #33
        Originally posted by Mudslinger View Post
        Pure and simple, give me a high to extremely high FOC and MOMENTUM over KE any day of the week!

        More accurate, more forgiving and a lot quieter bow. And if you want to talk drop at extremely long distances, give me the above!
        Yep my arrow I hunted with this week end was .610 momentum. Arrow is 566gn. No hogs so all I got to test it on was a turkey. Never Found my arrow.

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          #34
          using the AMO Method. DO you have the tip in to find the balance point?

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            #35
            Yes, leave in tip. Two ways to do AMO FOC calculation: 1. (recommended) measure from knock point to back of field tip; 2. measures from knock point to end of field tip. Both leave in point for balance purposes, then you subtract the difference of midpoint measurement and balance point, Put numbers into calculator and you'll get FOC %. Pushbutton you are on the right path. Dr. Ashby has conducted tests with thousands of shots on actual animals (usually fresh kills) over the course of some 25 years. I believe the Alaska Bowhunter Supply commercial site has his reports as well as a forum called Traditional Bowhunter. By the way, when I increased the weight and FOC of my arrows, I only had to cut about half an inch off to maintain spine stiffness. (However, I'm shooting a 50# recurve, and the arrows were Warrior 400s at 32 inches to start with, and my drawlength is 27-1/2"). Ashby's research also finds heavy and high FOC arrows used by Papua New Guinea tribes(in person field research) and North American Plains Indians (weighed and measured museum arrows).

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              #36
              Originally posted by muddyfuzzy View Post
              KE didn't increase in a linear fashion because velocity is squared in the formula. Logic (and basic physics) dictate that a increase in projectile weight will be accompanied by a proportional decrease in velocity all other things being constant(which they are I assume). You can't compare the two, the math is simply too different. I agree with what you are saying in principal but there is no mystery to the equation, it's basic math.
              The only thing I don't agree with is that the reduction in velocity isn't necessarily constant. At heavier arrow weights my bow outperforms the calculators and underperforms projections with lighter arrows. The bow is more efficient with more resistance. Even so, with the same broadhead I know that a 580 grain arrow at about 260 fps is going to penetrate better against a tough target than a 480 grain arrow at about 290 fps (which is to say nothing about their relative adequacy or merits), yet the kinetic energy is virtually identical. Using momentum you can get a much better idea about the penetrative potential and make more accurate predictions about real-world performance than you can with KE...

              But it's all nitpicky BS to a large extent. We should all just be shooting what we like to shoot, killing stuff and eating it.

              Comment


                #37
                Originally posted by JimboBurnsy View Post
                The only thing I don't agree with is that the reduction in velocity isn't necessarily constant. At heavier arrow weights my bow outperforms the calculators and underperforms projections with lighter arrows. The bow is more efficient with more resistance. Even so, with the same broadhead I know that a 580 grain arrow at about 260 fps is going to penetrate better against a tough target than a 480 grain arrow at about 290 fps (which is to say nothing about their relative adequacy or merits), yet the kinetic energy is virtually identical. Using momentum you can get a much better idea about the penetrative potential and make more accurate predictions about real-world performance than you can with KE...

                But it's all nitpicky BS to a large extent. We should all just be shooting what we like to shoot, killing stuff and eating it.
                there are things (like broadhead desgin) which have a much greater impact on terminal performance of an arrow regardless of FOC, momentum and/or KE. these are simply numbers based off calculations. most properly tuned bows are more efficient with a heavier payload, this we know. a great example of this is the manifestation of hand shock or added noise on the release in a bow using a lighter payload. the most important thing to remember here (and i like having these discussion btw) is that these numbers are simply reference points. while they may give us some insight into terminal perfromance they by no means are a be all end all. i will build arrows based on what my customers want first and foremost, all i can do is point them in what i believe to be the right direction. i get some crazy requests, but to each is own.

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                  #38
                  Originally posted by JimboBurnsy View Post
                  The only thing I don't agree with is that the reduction in velocity isn't necessarily constant. At heavier arrow weights my bow outperforms the calculators and underperforms projections with lighter arrows. The bow is more efficient with more resistance. Even so, with the same broadhead I know that a 580 grain arrow at about 260 fps is going to penetrate better against a tough target than a 480 grain arrow at about 290 fps (which is to say nothing about their relative adequacy or merits), yet the kinetic energy is virtually identical. Using momentum you can get a much better idea about the penetrative potential and make more accurate predictions about real-world performance than you can with KE...

                  But it's all nitpicky BS to a large extent. We should all just be shooting what we like to shoot, killing stuff and eating it.
                  note to self: throw away the calculators and get a good chrono.

                  Comment


                    #39
                    Originally posted by muddyfuzzy View Post
                    note to self: throw away the calculators and get a good chrono.
                    A Shooting Chrony alpha isn't a bad option if, like me, you can't afford an Oehler... More "fliers" and you need a larger sample to get the same data quality, but it generally tracks reasonably well with the top of the line.

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                      #40
                      Originally posted by muddyfuzzy View Post
                      note to self: throw away the calculators and get a good chrono.
                      Totally agree. All the numbers I posted above where through a chrono.

                      My bow starts gaining above 500 gn and really gains at 1080 gn. According to a calculator. My bow will shoot a 1080 at 71.7 fps. It shot it at 187 ft. You have to tell the calculated my ibo is 475 fps for that to work out.

                      That arrow is for the small white tail. Just want to make sure it makes a pass through.

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                        #41
                        So I spent some time quizzing one of our guys at work with a PhD in physics. Turns out I should be quieter with some of my opinions. Lol. Not the first time. Momentum wins due to impulse changes and force of impact. So heavy will always out penetrate light out of the same bow. All that is left is balancing the trajectory trade offs.

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                          #42
                          But what are the trade offs. I've been shooting in the low to mid 500 gn arrows. While doing some testing the other day I was thinking something was wrong with my bow. Loud at the shot. Went and checked the arrow I was testing. It was around 435. Dang what a difference in sound with a 100 gn extra.

                          You always see where people post that lighter arrows are better in case you miss judge your yardage. But in all reality. Most of us hunt from a stand and feeder at a none yardage. At that point speed does not matter.

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                            #43
                            Originally posted by muddyfuzzy View Post
                            there are things (like broadhead desgin) which have a much greater impact on terminal performance of an arrow regardless of FOC, momentum and/or KE. these are simply numbers based off calculations. most properly tuned bows are more efficient with a heavier payload, this we know. a great example of this is the manifestation of hand shock or added noise on the release in a bow using a lighter payload. the most important thing to remember here (and i like having these discussion btw) is that these numbers are simply reference points. while they may give us some insight into terminal perfromance they by no means are a be all end all. i will build arrows based on what my customers want first and foremost, all i can do is point them in what i believe to be the right direction. i get some crazy requests, but to each is own.
                            If I may I would like to add a bit to this discussion. I believe, when were talking penetration, that if you have an arrow that does not have all the mass behind it, i.e. properly tuned for optimum straight arrow flight, then you loose the power of the arrow mass, speed and wt. If that arrow goes in a bit off center then it does not have the force, be it KE or Momentum, to drive that BH as efficiently as it should. Tuning is just as important as the other factors. I am following and this is very interesting, by now you all know I am not one of the techy's on here. Watching, listening, learning, thinking.

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                              #44
                              Yes tuning is a major factor in this. So is correct spine. We all can get a weak arrow to shoot bullet holes. Flight is great. But penetration is bad. Then we start blaming the broadheads. But what is happening is that when the arrow makes contact with the animal the weak arrow will flex which now causes the shaft to hit the animal side ways. This is what causes bad penetration. Easy to see. Get a tuff target. Shoot a stiff arrow in to it and watch the shaft. Then shoot a weak arrow and watch. It looks like a antenna after you bent it over and let go.

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                                #45
                                There is very good info on this thread when It comes to arrows. I am knew to the FOC game. But muddy got me straightend out and built me some great arrows they are some hard hitting SOb'S!

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