Originally posted by enewman
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Originally posted by Mudslinger View PostPure 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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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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Originally posted by muddyfuzzy View PostKE 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.
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.
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Originally posted by JimboBurnsy View PostThe 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.
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Originally posted by JimboBurnsy View PostThe 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.
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Originally posted by muddyfuzzy View Postnote to self: throw away the calculators and get a good chrono.
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Originally posted by muddyfuzzy View Postnote to self: throw away the calculators and get a good 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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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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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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Originally posted by muddyfuzzy View Postthere 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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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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