MTLabrador
Well-known member
That’s the exact same bow setup I have, except I’m shooting 5mm FMJs and 125 viper tricks.Bowtech carbon night 70# draw 29.5" length
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That’s the exact same bow setup I have, except I’m shooting 5mm FMJs and 125 viper tricks.Bowtech carbon night 70# draw 29.5" length
watch those fmj man. I found over the course of a year of use they all bent slightly on me. But I'm almost set on switching to 5mm axis match.That’s the exact same bow setup I have, except I’m shooting 5mm FMJs and 125 viper tricks.
That’s what I’ve heard. I lost most of them shooting at grouse before I got a chance to find out. I’m due for new arrows this summer and probably going to the 5mm Axis with a heavier broadhead, maybe a cutthroat.watch those fmj man. I found over the course of a year of use they all bent slightly on me. But I'm almost set on switching to 5mm axis match.
And that's one reason I'm real hesitant on these high end arrow/broadhead setups. you lose a couple in a season and you just lost 1/2 the cost of the new bow!That’s what I’ve heard. I lost most of them shooting at grouse before I got a chance to find out.
And I've lost one for certain to poor penetration, where I just missed the mark and drilled the shoulder bone somewhere near the base of the blade
Care to share? I'd love to read more
Bowtech carbon night 70# draw 29.5" length
Understood, but the data I shared above (among many other datasets out there) shows that KE typically increases with arrow weight (despite the fact that velocity is squared in the KE calculation). I've seen KE vs. arrow weight datasets that went beyond 1000 gr, and KE was still increasing even at absurdly heavy weights. The explanation for why this happens is simple: a greater percentage of the potential energy stored in the bow during the draw cycle gets transferred to the arrow as the arrow grows heavier while a lower percentage of the PE gets "lost" to acceleration of the string, cables, cams, and limbs. In other words, the bow becomes more efficient at converting PE to KE as arrow weight increases.You have to remember that velocity is squared in the energy formula so if a bow slows significantly due to a heavy arrow, ke will decrease.
Interesting. Thanks for explanationUnderstood, but the data I shared above (among many other datasets out there) shows that KE typically increases with arrow weight (despite the fact that velocity is squared in the KE calculation). I've seen KE vs. arrow weight datasets that went beyond 1000 gr, and KE was still increasing even at absurdly heavy weights. The explanation for why this happens is simple: a greater percentage of the potential energy stored in the bow during the draw cycle gets transferred to the arrow as the arrow grows heavier while a lower percentage of the PE gets "lost" to acceleration of the string, cables, cams, and limbs. In other words, the bow becomes more efficient at converting PE to KE as arrow weight increases.
I'm not arguing for ultra heavy arrows...just for sound physics
Understood, but the data I shared above (among many other datasets out there) shows that KE typically increases with arrow weight (despite the fact that velocity is squared in the KE calculation). I've seen KE vs. arrow weight datasets that went beyond 1000 gr, and KE was still increasing even at absurdly heavy weights. The explanation for why this happens is simple: a greater percentage of the potential energy stored in the bow during the draw cycle gets transferred to the arrow as the arrow grows heavier while a lower percentage of the PE gets "lost" to acceleration of the string, cables, cams, and limbs. In other words, the bow becomes more efficient at converting PE to KE as arrow weight increases.
I'm not arguing for ultra heavy arrows...just for sound physics
That's a great explanation and the only thing I'll add is that you generally also get a higher conversion of energy from your bow string to your arrow with a heavier arrow due to the slower speed and thus longer duration of the energy transfer.Engineer chiming in, so fair warning to skip this, or grab a snack, settle in, and take this with a grain of salt.
Energy is neither created nor destroyed, it just changes forms. You draw back a bow, and that stores potential energy. You release, and the potential energy is transferred into kinetic energy (arrow flight and vibration). That's the simple application of the first law of thermodynamics.
Heavier arrows will have the same mass*velocity^2 KE as a lighter arrow. EXCEPT! The arrow is heavier, so it's going slower, and that means less velocity on your string and limbs, less vibration amplitude, and a more efficient energy conversion.
Heavy arrows, according to the applied laws of thermodynamics, have slightly, but not significantly, greater KE out of the same setup. I've seen this in my setup, as well as several others.
NOW. We get into momentum and inertia. Momentum is the applied, numerical value we assign to inertia. Which is an objects inclination to maintain velocity (speed and direction). Or conversely- the force required to stop an object in motion. It's mass*velocity. Notice that it's not squared. So with the same KE and higher mass, you wind up with significantly higher momentum. Meaning it takes more force to stop the arrow.
Back to that whole "maintain velocity and direction" bit- especially the direction. More momentum means less likely to change direction (deflect). You hit a rib, it wants to go through instead of deflect. You hit a shoulder, same thing. And it also means more force required to stop the arrow. So for the same KE, the heavier, slower arrow will take more force to stop. And if your broadhead has the same cutting area, the slower arrow will penetrate deeper, in any material.
Drag. Drag slows arrows. It is a function of half the velocity squared. So the faster arrow sheds velocity faster. And therefore sheds KE faster. So if two arrows start with the same KE, the lighter, faster arrow loses KE (and therefore sqrt velocity& momentum) faster as it goes downrange. The heavier arrows maintain more KE and momentum at range. I see this touted a lot, and most folks have it backwards. That being said, it's a minor actor, and helical vanes instead of angled do more to reduce drag than arrow weight.
The big downside to heavy arrows is slow speed, and more arch in the trajectory. That's it. That's the only thing. They go slower, take longer to cover horizontal distance, and drop more per 10 yards than lighter arrows. Judging flat line distance becomes damn near critical.
My bow (Reign 7, 70# @ 29.5") shoots a 442 gr arrow at 299 fps, 542 @270fps, and 642gr @239fps.
Trajectories, dropping from 0" @ 0 yards:
Range. 30, 40, 50, 60 yds
442 gr -18, -34, -52, -77 in.
542 gr -22, -42, -63, -92 in.
642 gr. -29, -52, -83, -118 in.
492 gr. -21, -37, -58, -85 (considering this one to add a little extra).
NOTE- when using a ballistics calculator, like above, you have to understand where you peak trajectory is. Here, it's at 0 yards. Typically it's 14-17 yards, since you're shooting slightly up from arrow level to sight line.
So when you're looking at trajectory calculators as the "end all, be all", you have to understand that the drop you're looking at in the table is at that distance PAST the peak height. So here, the "30 yd" value more accurately corresponds to 45-50 yards at the range. Go try it sometime- shoot with your 20yd pin level on the top of a target out at 30-40 yards, then measure how far down the target your arrow impacts. Don't believe me? Try it at 20 yards, and watch half your shots go sailing into nothing over the top, instead of being 8" down.
I'm not advocating either way on arrow weight, but I'm trying to explain the physics behind why you want one or the other. And a lot of the drawbacks are really overblown under 50 yards. Ideally? Infinitely heavy arrow for penetration going infinitely fast for ease of shooting. But there are tradeoffs, and there's a happy medium. Mine is probably the 490-550 range, but that will require field verification. And I quit going to a certain shop because they all but called me an idiot for looking to add 50-100gr to my arrows, then turned around to try selling me expensive, (and heavy) inserts.
No matter what you do, I'm a big fan of the "Trick-pin" holdover method for big game. Just use my 50yd pin on the keel of an elk, and that results in a 6" window on the vitals centered 12" up, from 11-42 yards. It's kinda nice. But that deserves it's own post.
That's a great explanation and the only thing I'll add is that you generally also get a higher conversion of energy from your bow string to your arrow with a heavier arrow due to the slower speed and thus longer duration of the energy transfer.
...yes.Rabbit hole warning- I feel like it's more an artifact of the slower speed rather than a cause of the increased efficiency. Higher arrow speed means the limbs are rebounding faster (and to higher amplitude), the cams are rotating faster, and the string moves farther forward (and to higher amplitude). All of these are forms of energy- kinetic energy while moving, potential energy when they pause to rebound (the noted amplitude). The faster/farther they move, the more energy they have- which is robbed from the total energy available to transfer to the arrow's KE. Slower speed comes first, which results in the things listed above taking less energy from the same starting total energy, more transferred to the arrow, and then higher efficiency. Longer duration is just the inverse of the slower speed in the system, making it an artifact of the speed. Or just a different way of looking at the same thing- time to cover a set distance, I guess. But it all starts with a heavier arrow.
Fancy way of saying "Vibration bad. Speed make more vibration. Slow good. I almost lost of train of thought, think I saved it at the end."
The one thing the process did teach me that I'm super grateful for was reading how my arrows were flying and what I should he looking for in a properly tuned setup. Now I'll move back to probably that 500-550g range with a sharp single bevel and an arrow that flies correctly and probably stick with that.
I used the 650 set up last season. Nice pass throughs on both the elk and the deer. I’ve pile drived some shoulders in the past with lighter set ups…my fault for poor shot placement. Looking forward to using them again this yr.I started with the grizzly stik 650 set up. Good product, they held up well. I would suggest building a few different set ups and testing them out on your bow. I spent about a month shooting different arrow set ups and I ended up with a 615 grain set up that has blown thru deer and pigs no problem. And I wouldn't hesitate to send it at an elk.
Sounds frustrating. What tuning method/s are you using?So @TrumpkinTheDwarf I'm back to own up. I've having a helluva time getting my bow to shoot accurately with these heavier arrows. Though, the end results was that my arrows are not all that heavy, nor is the FOC all that high. I thought I'd found easy success and had been shooting field points as well as I have had, or better. But they didn't always look like they were flying good even when they were hitting good. I finally put on my broadheads (125 cutthroats) and holy FUGGN' hell shit went sideways. Going back to the tuning board now.