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Arrow Weight Speed and Trajectory



By: HockeyDad
Posted: 21-Mar-11

Hello All - I am needing to increase my arrow weight - The problem is trying to evaluate the impact things will have on the overall speed, trajectory, quiteness and Tunability of the arrow. I am not a competative 3d shooter and will be hunting Elk and Mule Deer. I have searched the forums and entertained myself for hours where different threads evaluate individual aspects of this equation, but very little discussion related to the entire equation.

Current setup Mathews Z7 28" 65# Shooting 5575GT 100gr tip 376gr total weight. Chronoed at 286fps. Will hopefully be shooting a Fixed blade cut on contact head like VPA or Montec.

I am wanting to get to 400-450 gr range. If I go to a 125gr broadhead, I am marginally spined. If I increase my Draw weight to 70, then I am marginally spined regardless of tip weight. If I go to a 150gr broadhead I need new arrows.

It looks like I am out of luck with my current arrows. How can I evaluate all the factors and get a representative idea of what a 425 or 450 gr arrow will shoot like at 65 and 70#. Above what speed does tunability of broadheads and bow noise become a issue.

Is there a "sweet spot" of speed that within which you get all the advantages without the disadvantages?


By: Bowfreak
Posted: 21-Mar-11

The only disadvantage to adding arrow weight is speed loss. Everything else is a positive. If you want to stay in the GT line, switch to the 75/95 and a 125gr. heads and you will be in that range.....probably around 425 grains.


By: 5MilesBack
Posted: 21-Mar-11

As long as you use a rangefinder or are extremely good at estimating, there is no downside to heavier arrows. Unless you're shooting really slow and still want 7 pins in your sight.


By: Matt
Posted: 21-Mar-11

Heavier arrows shed less speed over distance than lighter arrows, so the trajectory impact isn't as great as you would think.


By: Beendare
Posted: 21-Mar-11

I am reading your question; what will the trajectory difference [and pin gap] be?

I bet if you post the specs of your current and proposed arrow someone will run it on one of those software programs for you to see......


By: HockeyDad
Posted: 21-Mar-11

Beendare: Right now I am trying to explore the possibilities of my proposed arrow configuration.

Current configuration Z7 28" 65# 375gr

Proposed Same draw but between 65-70# draw and arrow weight between 425-450gr.

Matt: Any trajectory calculators out there?


By: AndyJ
Posted: 21-Mar-11

HockeyDad- I just went through this exact same dilema and have come up with a solution that might work for you as well as it did for me. I shot 65#, 29" draw, 100gr tip, 5575 goldtips. My arrow weighed in at 389 grains. To get to a heavier arrow I switched to easton FMJ 400s, but I had a really hard time tuning them, then I switched to an FMJ 340 and same deal. I had a hard time getting it to tune. I increased my draw weight to 70#, which helped. Now my problem was my pins were way more spread out than I liked. I switched arrows again to easton st axis 340s (9.5 gpi) and am now wondering where they have been all my life. My arrow now weighs in at 430ish grains and my pins are as tight as they where with the goldtips. I have been in many situations where I have not been able to use my rangefinder and I plan to be in many more. A heavy arrow has it merits, but spreading my pins out is a huge disadvantage to me and it sounds like you feel the same way. I hope this helps.


By: x-man
Posted: 21-Mar-11

Trajectory calculators are just guesses with archery. The length and offset/helical on the fletching can make more of a speed difference than 5# or 15 grains will. There are just too many variables.

The better YOU are at shooting, the smaller the vanes can be, and the less offset/helical you will need, resulting in a flatter trajectory. But only you can answer that for yourself. It's better to error on the safe side I believe.

Definitely go to the next heavier spine arrow, increase the length of the arrow as needed, and increase the point weight. If you have a favorite arrow shaft(or two, or three), I would be glad to give you some setup options.


By: Trophy8
Posted: 21-Mar-11

HockeyDad....First I have to say don't over think the issue, 2nd your shooting ability will effect what result in pin gap you actually see.

Yesterday I was shooting indoors at 25yds (60lbs @ 29") 3 arrows with a 125gr TP vs 3 with 150gr TP...the difference between the groups was 1" at the most.

Another example...while shooting indoors at 35yds (arrow weights from 375-440grs) all the arrows grouped within a 2" circle. I did this just to show someone at the range just how minor the difference really was, he too was thinking the difference would be great.

Take into consideration you increase draw weight to 70lbs, a 425gr arrow will will most likely hit within 1" of your 376gr arrow, and I would bet a 450gr arrow won't be that far off. The trajectory of the arrow will carry the same flight out to about 50yds.

My point is don't get caught up thinking your pin gap is going to change drastically, once adjusted, you probably won't notice the difference.


By: Jaquomo_feral
Posted: 21-Mar-11

GREAT article on weight/speed/trajectory by Chuck Adams in the most recent Bugle magazine. Very much of an eye-opener for people who tend to underestimate the effect of trajectory when distance is misjudged by only a few yards.


By: 5MilesBack
Posted: 21-Mar-11

Yes, trajectory can be significant with misjudging distances. Shooting 3D shoots will show you that, and that's with lightweight arrows. Misjudging with my hunting arrows makes a significant difference. That's why I prefer to always have a ranged distance if possible. If nothing else, the added confidence of KNOWING the distance versus guessing the distance makes me shoot better.


By: dafish
Posted: 21-Mar-11

Okay he is not asking about 3D competition he is talking about hitting a 9-12 inch pie plate at any given yardge. I shoot 60# 28 inch- for Deer X-weave 200 w/100 gr broadhead 365gr at 272fps for Elk X-Weave 300 w/125 gr broadhead 425gr 258fps. Out to 30 yards without moving a pin I am with in 1 inch of each arrow. I do move the 50 and 60 yard pins a little. Not to hit the pie plate but to hit the dot so if I misjudge the yardage I will still hit the pie plate.


By: bow_dude
Posted: 22-Mar-11

Spend the 35 dollars or so, and buy yourself a computer program. I would recommend T.A.P. and then you can play with the options and get your answers. Much cheaper to purchase a program than buy new arrows. They are amazing how accurate they can be. I think T.A.P. is the most user friendly. I change arrow configurations all the time to match up to what I am doing. Printing out a sight tape to set the pins is as simple as it gets.

As far as hitting the 9 to 10 inch pie plate... I suppose if that is as accurate as you want to be, so be it... it works. I once read an article written by Randy Ulmer. He said that close is not good enough, he likes to be right on. I have the same opinion. I want to be exact, not "close enough".


By: kanbm
Posted: 22-Mar-11

Where the weight is added can make a big difference in the affect it has on trajectory as well as it's benefits in regards to penetration. Take a look at the papers written by Dr. Ed Ashby for a much more detailed and indepth analysis than I could ever give.


By: HockeyDad
Posted: 22-Mar-11

Thanks for all the info so far - Lots of interesting thoughts.

One additional question - My current arrow GT 5575 weighs 376 grains. It is 29" long. So 29 * 8.6 = 249.4. Add in a 100gr tip thats 349.4. Insert @ 11.4 and nock at 11.5 brings me to 372.3

That leaves 3.7 grains for the 3 vanes that I have. On the GT Site, they list the 1.5" HP Vanetec vanes at 3.1gr - I thought that would be weight for each vane, not a set of 3. Somewhere I am missing a few grains.

Now to find the combination arrow/tip that will get me to 425-450gr range with a 125 or 150 gr broadhead...


By: SDHNTR
Posted: 22-Mar-11

I shoot a very similar setup with 28" arrows. Gold Tip 7595s with VPA Terminator 125s. Total weight is about 427. They fly beautifuly. Out of my Destroyer 340 I am getting about 285-288 fps. The effect on game with that combo has been excellent. Pass throughs on everything, including elk.


By: HockeyDad
Posted: 22-Mar-11

SDHNTR - Are you shooting the black 7595's or the camo ones? The gpi varry depending onthe finish: 8.9 - Black and 10.2 - Camo.

Also what vanes are you using to ensure stabilization: The 1.5" HP Vanetecs or something else?


By: Tracy
Posted: 22-Mar-11

Speed don't kill. I get passthroughs with my longbows and recurves. The 550 grain arrows are only going an average of 175 fps. Who needs a super fast arrow? I would rather have a quiet bow myself.


By: SDHNTR
Posted: 22-Mar-11

I'm shooting black arrows. The camos ones are too hard to pull from a target. I use AAE Max Hunter Vanes. Fletched on an AZ EZ Fletch mini for a good bit of helical and offset.


By: Kawabunga
Posted: 22-Mar-11

I was shooting the camo 75/95s and had a weight of about 480 grains with a 125 head, like the 425, 450 range also. I think camo 5575s would work, had MFXs in that range and loved em looking at the new Kinetics also.

With the heavier setup my pin gaps were huge, as X-man said I think I have to look into my vanes as I'm shooting 3.5" Quckspins, like them but suspect they have some some serious drag. I used to think it didn't matter with a rangefinder but sometimes I'll range something close to an animal so the yardage may not be perfect, and with less than perfect form a little high or low you could be off that cirlcle a lot faster.


By: x-man
Posted: 22-Mar-11

"That leaves 3.7 grains for the 3 vanes that I have. On the GT Site, they list the 1.5" HP Vanetec vanes at 3.1gr - I thought that would be weight for each vane, not a set of 3. Somewhere I am missing a few grains. "

Did you weigh your shafts before you built them? The 8.6 gpi is an "average" that Gold Tip has in that shaft spine size, not an absolute weight.


By: HockeyDad
Posted: 22-Mar-11

I found some nice web sites that can do speed and trajectory approximations/estimations. And got adventurous on some "Estimations".

Speed Calc: http://backcountrybowhunting.com/articles/calc/ Trajectory Calc: http://www.outdoorsden.com/archery/archbal.asp

The speed calculator estimated the same fps that I chronoed with my bow - so it gave me a little bit of a comfort factor with the numbers I was seeing.

So I used the speed calculator to determine approximate speeds for my current setup 375gr arrows at both 65 and 70# draw weight as well as 425gr arrows:

375 @ 65# = 288 @ 70# = 298 425 @ 65# = 273 @ 70# = 283

I then went to the trajectory calulator andtried to factor in 2 exagerated "Missjudged Yardage scenario" What if I used the 20 yard pin at 40 yards and the 30 yard pin at 40 yards. here is the results 20/40 - used the 20 yard pin at 40 yards - inches below aiming point that arrow impacted 30/40 - used the 30 yard pin at 40 yards - inches below aiming point that arrow impacted

20/40 30/40 375 @65# -17.0 -8.9 375 @70# -16.5 -8.3 425 @65# -19.7 -9.9 425 @70# -18.3 -9.2

So what this is showing me, is that adding 50 grains to my arrow will affect my point of impact in the 20/40 scenario by 2.7" and 30/40 by 1" without changing draw weight. If I bump my draw weight up to 70# I will be altering my point of impact by even less - 20/40 = 1.3" and 30/40 = 0.3.

What I was trying to evaluate here was Given the 2 setups 375@65 and 425@70 what would a missjudges range do to my shot - basically nothing.

So just to see what the differences were in the 2 setups to the overall trajectory - I used the trajectory calculator with a 0 yard pin. Below are the 40 yard points of impact

375 @65# -33.8 375 @70# -31.6 425 @65# -37.7 425 @70# -35.1

** For grins I ran 450 @70 and got a drop of 36.9 **

The difference between 375 @65 and 425 @70 are minimal ~ 1.3 inches. Being able to bump the draw weight to 70# appears to have a very positive impact to the equations...

Given the data above 70# GT7595's and a 125gr broadhead shouldn't change things too awful much in the trajectory arena - but should provide a lot of improvement on whatever I hit.

Any Thought? Comments?


By: wildwilderness
Posted: 22-Mar-11

If you want to keep your GT5575 you can probably cut off 1" since you said your draw was only 28" that would stiffen the arrow then you could go to a 125gr head and end up with about a 395gr arrow. and still shoot 65#

The other option to keep your current arrow and not cut them (if you don't have any room left to shorten them) is to drop your poundage to say 60# and go with a heavier tip 125, give you a 400gr arrow but a bigger pin gap.

A couple years ago had a similiar set up- 30" draw 63# bow with GT 5575 cut to 28.5" with 100gr tip for about a 375gr arrow. This worked great on whitetails. It was marginial on spine so when I moved to elk country again I bumped my poundage up to 68# and went with a 340 spine easton st epic nano at 29" and stuck with a 100gr bh since I had a bunch. The arrow goes about 425gr. I have been leaning toward a 125 gr tip to give me a 450gr arrow which may help a bit with elk.

I would get a new stiffer arrow which would inherently put you over the 400gr point. bump your poundage up a couple pounds if you are worried about pin gap, but bottom line accuracy is more important than speed.


By: HockeyDad
Posted: 22-Mar-11

Whoa crap - my chart data didnt appear very well. How do I get the formatting to appear?

Hopefully its a double enter

First Chart 20/40 30/40

375 @65# -17.0 -8.9

375 @70# -16.5 -8.3

425 @65# -19.7 -9.9

425 @70# -18.3 -9.2

40 yard zerod at 0 yards 375 @65# -33.8

375 @70# -31.6

425 @65# -37.7

425 @70# -35.1


By: dafish
Posted: 22-Mar-11

+1 Tracy Shooting 278fps is lot faster then I have every used to shoot Elk or Deer. I would shoot what you have now as a heavier broadhead does not give a larger cutting area. I have killed Elk with a recurve shooting Easton 2117's and also out of a compound shooting 224fps and that was a fast bow back then. Keep it simple.


End of Topic
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