Too heavy? Arrow building

[Buffalomtn]

Over the last five years I have tested at least 20 different compound bows through an Oehler 35 P chronograph. Arrow weights varied from 350 grains to 700 grain with several arrows in between those weights. I have yet to test one that the KE did not increase at least slightly from light to heavy arrows. Have never tested one that had the KE decrease as arrow weight increased.
Results to the contrary could be explained by the variances (incorrect readings) often recorded with typical archery shop chronos or too weak of spine as point weight is increased. Have seen Pro and Shooting chronos read different with back to back shots of the same arrow with different color fletching. If you are seeing KE decrease as arrow weight increases it is likely for one of the reasons stated above and certainly not to be expected or the norm.

 

[N2TRKYS]

Over the last five years I have tested at least 20 different compound bows through an Oehler 35 P chronograph. Arrow weights varied from 350 grains to 700 grain with several arrows in between those weights. I have yet to test one that the KE did not increase at least slightly from light to heavy arrows. Have never tested one that had the KE decrease as arrow weight increased.
Results to the contrary could be explained by the variances (incorrect readings) often recorded with typical archery shop chronos or too weak of spine as point weight is increased. Have seen Pro and Shooting chronos read different with back to back shots of the same arrow with different color fletching. If you are seeing KE decrease as arrow weight increases it is likely for one of the reasons stated above and certainly not to be expected or the norm.

Nope, not always. Heck, it’s even in the some of info that MM posted. It’s not hard to understand that all things are exacts.

 

[Bmoore]

Nope, not always. Heck, it’s even in the some of info that MM posted. It’s not hard to understand that all things are exacts.

Not sure what you mean by this? All the data MM posted shows increasing KE with arrow weight.

 

[N2TRKYS]

Not sure what you mean by this? All the data MM posted shows increasing KE with arrow weight.

Not in the second thing that he posted. If you use their rules of thumb, some had a KE that did decrease. I just picked one at random, so I don’t know how the others played out.

 

[Bmoore]

Not in the second thing that he posted. If you use their rules of thumb, some had a KE that did decrease. I just picked one at random, so I don’t know how the others played out.

If you do the math on all five there’s some individual fluctuations however the KE starts at 68.00 and increase to 68.61 for the 450 grain arrow. The data points fluctuate but the general trend is still increasing.

 

[Bmoore]

also, based on the speeds and arrow weights you posted you losing speed at a greater rate than normal. According to that second article MM Posted, there’s a 1-1.5 FPS loss for every 5 grains of arrow weight. According to the numbers you posted your over 2.6 FPS loss for every 5 grains added. That sounds high and not generally on trend. That can help explain why your setup losses so much energy. None of this is to say you should change anything, only that the math your getting is certainly atypical.

 

[nphunter]

Arrow flight/accuracy is the most important factor followed by self confidence.

I’ve killed a bull with a 330gr arrow coming from a 60lb bow with 27” draw with a chisel tip fixed head and got a pass through on that bull at 53 yards. Most of my elk hunting has been done with a 390-420gr arrow flying over 300fps and up to 315fps. I had very few options for fixed heads at those speeds, tuning and building very tight spec arrows with high quality heads become very necessary at over 300fps.

Curently I’m shooting 500gr at 278fps with a large cut expandables, it’s very forgiving and accurate but there is a huge difference in trajectory difference compared to the above builds. If every state I hunt allowed expandable heads I’d drop back down to mid 400’s and pick up some trajectory. Since I have to shoot fixed heads I want as forgiving as a setup and I can get within reason. I try to stick around 280fps for that reason, it also makes it nice to be able to leave my pins alone and set my speed accordingly with arrow weight. Currently to get to 500gr I have to add brass and collars to my arrows.

 

[Savagenut]

KE formula is velocity squared.

Kinetic Energy Calculator

If you know the mass and velocity of an object, use the kinetic energy calculator to find its energy in movement.

www.omnicalculator.com

 

[cuttiebrownbow]

Part of what determines my arrow weight is also my bow’s noise. I would rather add 50 grains to my arrow weight and deaden out my bow then add stuff to my string. I like a quiet bow so that’s important to me.

Adding string leeches, monkey tails and spiders all work well but I find a heavier arrow works just as well. You will lose speed either way but at least with a heavier arrow I losing speed but gaining penetration power.

I have a 27.5 inch draw and shoot a 70-72lb bow. I end up in the 450-500 grain range. 500ish for my whitetail set up but I like to go down to 450s for big game. I like the pick up of speed for longer distance shots and stay at 280 or even a little faster.

QAD exodus and Muzzy Trocars both work well for me.


I feel very confident with my 450 grain arrow going 280 on anything I would be hunting.


Sent from my iPhone using Tapatalk

 

[HighUintas]

Good god. Set up the arrows spined correctly and in the middle of the range and practice shooting more.

 

[Mighty Mouse]

If you do the math on all five there’s some individual fluctuations however the KE starts at 68.00 and increase to 68.61 for the 450 grain arrow. The data points fluctuate but the general trend is still increasing.

I noticed the same thing in the data from the Petersen's article: small fluctuations but a general trend of KE increasing with arrow weight. Attached is a plot of the Petersen's data with a linear trendline applied. The increments of arrow weight are so small (5 gr) that speeds being off by less than 0.5 fps could give the appearance of decreasing KE between some data points. With every chronograph I've used (at least 3 different makes/models), it's not uncommon to see 1-2 fps variations across consecutive shots with the same arrow. A wider range of arrow weights helps mitigate error/uncertainty in speed measurement and shows the KE trend more clearly (as seen in the other 2 datasets I posted).

 

[N2TRKYS]

If you do the math on all five there’s some individual fluctuations however the KE starts at 68.00 and increase to 68.61 for the 450 grain arrow. The data points fluctuate but the general trend is still increasing.

Not for all of them. Rules are thumbs are great, but as proven here that you need to verify for true results. Which was the point all along.

 

[Buffalomtn]

Not for all of them. Rules are thumbs are great, but as proven here that you need to verify for true results. Which was the point all along.

You should verify your test again. What is you set up and what weight/spine arrows did you test. Highly unlikely that you would be able to repeat the test and come to the conclusion that lower weight arrows increase KE. Likely you observed the inconsistencies that are inherent in the typical chronos used in an archery shop. If you are using lighter weight arrows so that you increase your KE you are fooling yourself. That said some guys don’t really want to know the truth, they just want to justify their preconceived notions.

 

[Bmoore]

Not for all of them. Rules are thumbs are great, but as proven here that you need to verify for true results. Which was the point all along.

I’m not sure I understand what your point is. The data clearly shows a gradual increase. As with all data sets there slight variability which can easily be accounted for in inconsistent readings from the chrono or slight difference in release by shooter or any number of things. That’s why the trend is important. You can’t look at two data points and assume that is the trend. You need to look at all the data. And as many others have pointed out, the data collected in nearly all cases ( you being the only exception I think) shows a gradual increase in KE with increase in arrow weight.

 

[MattB]

A friend ran an archery shop for decades and did this sort of testing on all sorts of bows. He would occasionally reference that certain cam system were either particularly efficient or inefficient with heavy arrows. With that, I think it would be foolish to ignore the possibility that some bows may generate lower KE with heavier arrows even though that is the general rule. The same as it is foolish to argue the rule based on the exception or that KE goes up as arrow weight goes down because velocity is squared.

 

[Billy Goat]

All of these data points are arrow weights up to 500 grains. Try some up around 750.


I have seen several bows loose ke after a certain point. Guy called me just a few months ago because he was surprised about heavy arrows in his recurve were actually giving him lower ke. Ashby talks about it in his report.

If I get time I'll run several arrows over a Chrono and post my results.

 

[5MilesBack]

All of these data points are arrow weights up to 500 grains. Try some up around 750.

Try some up to 1500gr. Pretty sure that's how high Widgeon went when he tested many bows with this. He said he never did find a bow that wouldn't gain KE with a heavier arrow to at least 1500gr. You definitely have to perfectly tune each bow to each new arrow to get maximum performance and a continual rise in KE.

 

[MattB]

Try some up to 1500gr. Pretty sure that's how high Widgeon went when he tested many bows with this. He said he never did find a bow that wouldn't gain KE with a heavier arrow to at least 1500gr. You definitely have to perfectly tune each bow to each new arrow to get maximum performance and a continual rise in KE.

Thw times I have tested this I have grabbed a bunch of arrows out of my bin without a consideration to spine, diameter, or anything and still demonstrated an increase in KE with an increase in arrow weight. No tuning at all, and I am fairly certain that the heavy arrows were quite weak from a dynamic spine perspective.

 

[Reburn]

All of these data points are arrow weights up to 500 grains. Try some up around 750.


I have seen several bows loose ke after a certain point. Guy called me just a few months ago because he was surprised about heavy arrows in his recurve were actually giving him lower ke. Ashby talks about it in his report.

If I get time I'll run several arrows over a Chrono and post my results.

Ive heard this about the bowtech SR6. Beast with 29-31" draws and 450-499 grain arrows. Go higher grain weight start shaving speed at an abnormally high rate. Shorter draw and never optimize the cams. This is just what I have read by bowtech prostaff as well. Havent tested it.

 

[N2TRKYS]

You should verify your test again. What is you set up and what weight/spine arrows did you test. Highly unlikely that you would be able to repeat the test and come to the conclusion that lower weight arrows increase KE. Likely you observed the inconsistencies that are inherent in the typical chronos used in an archery shop. If you are using lighter weight arrows so that you increase your KE you are fooling yourself. That said some guys don’t really want to know the truth, they just want to justify their preconceived notions.

Never said I was chasing KE. I was just reporting my repeated results taken on several different days.