More accurate at short range with lighter arrows?

[Benny Nganabbarru]

I'm not sure, but I think I've noticed something about the accuracy of my shooting, even at close range, improving as I shoot lighter arrows. All arrows are well-tuned. By light, I mean 8 to 10 grains per pound. That's comparing them to arrows that are around 12 grains per pound. I seem to get tighter groups, even up close. Is there any chance that the arrow being affected by the bow for a shorter amount of time makes it influenced less by my release faults? Or am I imagining this? Penny for your thoughts...

[richbear]

Hope someone chimes in Ben. I've wondered the same thing for along time and have noticed the same results with lighter arrows at shorter yardages.

[tradtusker]

i think with the greater speed there is less effect on the trajectory, iv noticed with a heavy arrow (700grs) it defiantly shows up if you hold a little high or low at the shot where as a light fast arrow does not show up the fault as much

that would be my first thought

is the group suffering high and low or is it left and right issues?

[Soilarch]

You all know I'm a newb to the trad world but in the compound world you'd get a thousand "YES" answers to question.

This is why fall-away, or drop-away, rests are so popular.

Less time in contact with the shelf/rest means less user input.  

"They" also say it makes arrow tuning less critical.  I haven't figured out the "why or how" of that, but IF it's true than your arrows that are tuned well...lets say at 1:00 on the "bell curve"...with a longer contact time are now at 12:00 with a shorter contact time.


Like I said, I'm not sure about the forgiveness of tune, but the less amount of time that arrow is touching the bow or string the less amount of time that WE have to mess things up.

Even more reason to shoot a heavy bow I guess?  Cleaner releases, and can get up there past the "magic" 650gr and still be at 8-10gpp.


Edit:  Perhaps the reason this is showing up more at short ranges is because of wind drifts?  I know the faster arrow is in the air for less time so it OUGHT to be affected less by wind drift...but it gets "blown" off course easier as well.  I do think wind drift has more effect than we think.  I could tell a big difference between my 4" feathers and 2" blazers if there was a moderate breeze. (Back in my compound days.)

O.L.    You got any ballistic coefficient comparisons for  light and heavy arrows that are otherwise similar?  Or any other crosswind 'goodies' from flight world?

[Bradd]

I think (not sure so I would like to know too) that it has a lot to do with trajectory, form errors, and brain function.

Trajectory:  This is why 3D shooters use faster flying arrows on the courses...less distance/wind error calculations.  It is also why indoor target shooters mostly use heavier arrows, where the known distance isn't a problem..point at the right spot and it will always it there.

Form/Release Error:  The arrow is getting out of noodle mode faster (it is less affected by the wind outside, and since the front is following the back it will appear to be straighter, which leads me to the next point...

Brain:  Because the heavier arrow is in the air longer and you can actually see the trajectory, the brain over compensates.  If the brain is tuned into a faster arrow, then it will shoot the faster arrow better...it's a confidence thing???

[DaveBriner]

Even more reason to shoot a heavy bow I guess?  Cleaner releases, and can get up there past the "magic" 650gr and still be at 8-10gpp.[/QB]

Heya Soilarch,
What's the "magic" 650gr?  Is this a critical mass to hit for good KE (= pass through's?)

Thanks,
Dave

[Soilarch]

Dr. Ed Ashby has done an exhausting amount of research on arrow penetration.  (Just type in "ashby" to the search engine)

One of the many factors he's tested is overall arrow weight.   It seems as though once arrow weight hits 650gr or more,  there's a significant improvement.

His studies are on/with Asiatic Buffalo where you need to get every ounce of performance (and penetration) that you can.

In short, this IS a mass some "shoot for" when getting there setups tuned. There's been a whole lota deer go down to lighter arrows, especially from compounds.  So don't go second quessing your setup, but it's a nice number to keep tucked away in the back of your head.


I called it "magic" because it seems like there shouldn't be one weight where things start to noticeably improve.  It should all be a gradual improvement.  Since I can't really explain it, and haven't ran across a good 'numbers' explanation....it's "magic" to me   :D

[OkKeith]

Ben,

I have seen this happen with my shooting as well. My thoughts are that given equal spine between a light arrow and a heavy arrow, the light arrow recovers from the archer’s paradox quicker than the heavy one. For me, this explains why this shows up at shorter distances.

I would think this condition would not show up with arrows that have differences in weight AND spine. I think in that case there are several other things going on.

Perhaps the mass of the heavy arrow influences how quickly it recovers. The heavy ends would whip back and forth longer before they "came to rest" so to speak than would the ends of the lighter arrow. Again though, given that both arrows have the same spine rating.

It may also have something to do with the arrow materials themselves. A 450 grain arrow and a 650 grain arrow, both spineing at 55lbs, will have different material characteristics. They may not even be the same type of material (cedar vs. ash vs. alum. vs. carbon).

Now... I am not a materials engineer or even an archery expert, although I have shot arrows in the parking lot while staying in a Holiday Inn (not sure if you get the joke in that, your TV commercials maybe different than ours).

Investigating this sounds like a good excuse to buy a spiral notebook, a few #2 pencils and shoot some arrows for data collection (as if you need more reasons to shoot arrows).

OkKeith

[Bender]

A 29" arrow drawn to 28" and shot at 170 fps clears the bow in .014 sec. Same length arrow shot at 180 fps clears the bow in .013 sec. You would have to be really fast at screwing up your shot for that to be the cause of the difference. However 10 additional fps can mean about 3" less drop at 20 yds. I got that 3" from using my own bow's number. Your mileage may vary as they say. Still it gives you an idea for comparison. The better groups from the lighter arrows (given correct tune for both the light and heavy arrows) is due to the flatter trajectory.

[Soilarch]

If my math is right....IF it's right:

Then 1/8" movement at the bow makes for a 2.5"@20 yards.  That's if we don't take into consideration that the movement may effect the requirements on the spine...so know we have 2.5"@20yards on top of what the difference in spine may do.  I think 1/8" is certainly realistic when you consider that you don't have to MAKE the bow move in .001 seconds you just have to LET the bow move in .001 seconds. Those limbs are moving sometimes a foot or more in that .001 seconds so the riser moving 1/96 of a foot starts to seem easy.

[Bender]

I believe your math is correct Soilarch. But consider this,since Kleinig is shooting the shorter arrows more accurately he is clearly able to "shoot the difference." He is a good enough shooter to take advantage of those things which can give him better accuracy. Following your idea (a good one BTW) that the shooter needs to not let the bow itself do something weird in that .001 sec then Kleinig is staying in control. If he weren't, he wouldn't be able to extract any advantage from anything. Even if we assume that he always had proper tune, long, short, heavy, light, etc etc wouldn't make any difference in his overall accuracy. I just believe he's taking advantage of the flatter trajectory. Your point is valid, but the flatter trajectory is something that is measurable, even at 20 yds. without having to resort to measurements/numbers on the order of thousandths of a second.
 Occam's razor, the simplest explanation is most likely the right explanation.

[OkKeith]

Bender,

I see your point but I am not sure the arrow speed is the answer. Shot from the same bow at the same draw length, a lighter arrow of equal length will travel faster than a heavy arrow of equal length. Absolutely and with out a doubt, but I think the flatter trajectory does not increase the accuracy.

I could be totally wet on this (not uncommon for me) but here is how I see it:

If we use the tip of the arrow as an aim point, we shoot the lighter arrow (say 400 grains total weight, equaling 8grs. per pound of bow weight) holding 2 inches above the bull’s-eye. With a clean release and everything else correct (I know, not very likely for me, but hey, it's an example) we get a 4 inch group at 15 yards.

Then, shooting a heavy arrow (say 650 grains total weight, equaling 13grs. per pound of bow weight) of the same length and spine, tuned just as well as the lighter arrow, we hold 6 inches above the bull’s-eye and get an 8 inch group.

As long as the aim point is consistent (2" above for the light arrow and 6" above for the heavy arrow) this is repeatable. We get tighter groups with the light arrows than with the heavy arrows at 15 yards shooting distance. Now, this is from my own experience.

To me, even though the lighter arrow is faster than the heavy arrow, using the consistent aim point says to me that there is some other thing going on besides the flatter trajectory helping out.

Could it be that the increased speed allows less time for me to screw up the shot? Maybe, but at 20 and 25 yards shooting distance, using a consistent aim point there is little to no difference in the size of my groups. The lighter arrow groups get a little bigger, and the heavy arrow groups actually get a little smaller. The speeds that the arrows leave the bow are the same at 15 yards as they are at 20 and 25 yards. This tells me the situation has something to do with the way the arrow is flying over that shorter distance, not in how fast it is flying.

I dunno. Like I said, I am not much of an expert and can only really report what I see with my own shooting. It's really only an interesting diversion for me since I don't hunt with the light arrows. I only use them for the occasional round of 3-d shooting.

What do ya think?

OkKeith

[Bender]

We know that a shooting machine will put the same arrow back into the same hole regardless of wether the arrow is "heavy" or "light". Whatever is going on has to do with the shooter, not the arrow. I just think that the flatter trajectory will be more forgiving of tiny errors than the difference of .oo1 second that the arrow is still passing by the riser, that's all.

[OkKeith]

Makes sense to me Bender.

What is good though, is that I don't have to understand it to take advantage of it.

So, have you seen this same thing with your shooting?

OkKeith

[Bender]

Yes I have with my tournament arrows. I have seen better accuracy at all ranges with my competition set up. I don't screw around with experimenting much with my hunting set up though. It works quite well for me and if it ain't broke don't fix it.