New arrow set up?

[Kbhillhunter]

It's that time of the year where I have too much time on my hands and start tinkering with my gear. Got a new bow this year, and have it tuned to shoot the arrows I've been shooting well for the last few years. I was surprised they were flying a little slower than I realized, so starting to question whether it's worth it to shed a little weight and pick up some additional speed. About 90% oft hunting application is for eastern whitetail, but I do archery elk every 1-2 years as well. About the only advantages I could think of would be a speedier arrow for jumpy white tails, better downrange speed for longer shots (50-60 yards out west), and possibly tightening up my pingaps a little.

Right now I'm shooting a black eagle carnivore 250 with a 100gr insert and 100gr head for total weight of 540gr. Speed is 250fps, FOC is about 14%, KE is about 77.

If I go with the same arrow in a 300 spine, 42gr insert, 100gr head, I can get weight down to 444gr which should put me at 285fps, KE of 80 and FOC of about 11.5%.

The specs on the lighter arrow set up seem pretty solid. But is it worth it to switch it up if my current set up shoots well, maybe just a tad on the slow side? Any factors I haven't considered?

 

[Mighty Mouse]

Hard to say how much your trajectory will improve without just trying it. Replace your current heavy insert (if you can pull it or cut it off) with a lightweight aluminum one and see what happens.

BTW your numbers are a bit off. KE will decrease (very slightly) if you decrease arrow weight. If your bow is doing 250 fps at 540 gr, I would estimate 275 fps at 444 gr.

 

[Kbhillhunter]

Hard to say how much your trajectory will improve without just trying it. Replace your current heavy insert (if you can pull it or cut it off) with a lightweight aluminum one and see what happens.

BTW your numbers are a bit off. KE will decrease (very slightly) if you decrease arrow weight. If your bow is doing 250 fps at 540 gr, I would estimate 275 fps at 444 gr.

I noticed that in the KE as well. I just used a calculator I found online and thought it was odd, I would have expected the same but figured maybe it knew something I didn't.

 

[big44a4]

It's that time of the year where I have too much time on my hands and start tinkering with my gear. Got a new bow this year, and have it tuned to shoot the arrows I've been shooting well for the last few years. I was surprised they were flying a little slower than I realized, so starting to question whether it's worth it to shed a little weight and pick up some additional speed. About 90% oft hunting application is for eastern whitetail, but I do archery elk every 1-2 years as well. About the only advantages I could think of would be a speedier arrow for jumpy white tails, better downrange speed for longer shots (50-60 yards out west), and possibly tightening up my pingaps a little.

Right now I'm shooting a black eagle carnivore 250 with a 100gr insert and 100gr head for total weight of 540gr. Speed is 250fps, FOC is about 14%, KE is about 77.

If I go with the same arrow in a 300 spine, 42gr insert, 100gr head, I can get weight down to 444gr which should put me at 285fps, KE of 80 and FOC of about 11.5%.

The specs on the lighter arrow set up seem pretty solid. But is it worth it to switch it up if my current set up shoots well, maybe just a tad on the slow side? Any factors I haven't considered?

A lot on the slow side for what I like. I don’t see a need for anything that heavy for the reasons you mention. Ever get in a spot when you need to judge yardage and don’t have time to range you better be good. I never look at FOC when I’m building arrows. I build for the weight/speed I want followed by components I want to use. Those are my 3 constraints. I try to be 280-290fps for hunting setup.

 

[TX_hunter]

I noticed that in the KE as well. I just used a calculator I found online and thought it was odd, I would have expected the same but figured maybe it knew something I didn't.

Did you use a calculator to come up with the 250fps reading? If you get actual chrono numbers with one arrow, then tweak the ibo in this calculator to get you the same speed as the chrono, it will be very accurate for checking other arrow weights:

Arrow Speed Calculator | Sirius Archery Products

This calculator is based on average efficiency gains as arrow weight is increased from 5 grains per pound (IBO). The most critical factor is the IBO speed

siriusarchery.com

 

[Kbhillhunter]

Did you use a calculator to come up with the 250fps reading? If you get actual chrono numbers with one arrow, then tweak the ibo in this calculator to get you the same speed as the chrono, it will be very accurate for checking other arrow weights:

Arrow Speed Calculator | Sirius Archery Products

This calculator is based on average efficiency gains as arrow weight is increased from 5 grains per pound (IBO). The most critical factor is the IBO speed

siriusarchery.com

The 250 speed was from a Chrono. I used a different calculator and just plugged string weight until I got to the chrono'd speed to match, then I plugged the weight of the new arrow set up im considering to see what that speed would look like

 

[Zac]

KE is a totally useless spec. I think I would prefer the 280 build. But that’s only for western hunting.

 

[Bigborealaska]

I noticed that in the KE as well. I just used a calculator I found online and thought it was odd, I would have expected the same but figured maybe it knew something I didn't.

Be careful with those online calculators. They get you an idea but are often off on the numbers. I shoot a mathews halon at 70# 29.5" draw and with a proper tune and new string shooting through a chrono my arrow speed with a 523gr arrow was 282 x 3. Calculator told me I'd be in the mid 290's

 

[Mighty Mouse]

I noticed that in the KE as well. I just used a calculator I found online and thought it was odd, I would have expected the same but figured maybe it knew something I didn't.

Many online calculators apply a flawed speed-to-arrow weight correlation and tend to underestimate the speed of heavier arrows. The calculator mentioned above on Sirius Archery's website is an exception; it does a good job of accounting for the actual relationship between speed and weight.

For all practical purposes, KE can be assumed to remain constant. So if you know your speed at a particular arrow weight, you can calculate KE then use that KE number to estimate speed at any other arrow weight: Arrow Speed (in fps) = SQRT[450,380 × KE (in ft-lbs) ÷ Arrow Weight (in gr)]

 

[MattB]

I would probably go for faster so long as dynamic spine was still good, but as previously stated your number are wrong. You won’t get more KE from a lighter arrow.

 

[Billy Goat]

My experience is with 100 grs you will be around 30-34 fps difference. I don't know that the numbers are that far off, speed wise. The KE should remain more consistent.

That's with 28-29" DL and 60-75ish pounds. I'm sure different sides of those numbers see different swings.

I like 280+ fps generally.

How long are the carnivores? IIRC I had 250's with 60 gr SS inserts and 125 heads and was still sub 500 gr, like 490 I believe. Lighted nock and wrap?

 

[Kbhillhunter]

My experience is with 100 grs you will be around 30-34 fps difference. I don't know that the numbers are that far off, speed wise. The KE should remain more consistent.

That's with 28-29" DL and 60-75ish pounds. I'm sure different sides of those numbers see different swings.

I like 280+ fps generally.

How long are the carnivores? IIRC I had 250's with 60 gr SS inserts and 125 heads and was still sub 500 gr, like 490 I believe. Lighted nock and wrap?

My draw length is 32.5 so I shoot them uncut at 32". I would drop down in spine from the 250 to a 300, then use the factory inserts which are 14gr, and switch to a 125gr tip which should get me to total arrow weight of about 440. My current arrow is 540 and actually chrono'd at 250. Every calculator I use shows speed going to about 285 with the lighter arrow, so that seems consistent with your findings too.

 

[MattB]

My draw length is 32.5 so I shoot them uncut at 32". I would drop down in spine from the 250 to a 300, then use the factory inserts which are 14gr, and switch to a 125gr tip which should get me to total arrow weight of about 440. My current arrow is 540 and actually chrono'd at 250. Every calculator I use shows speed going to about 285 with the lighter arrow, so that seems consistent with your findings too.

Backing into an estimated fps for the 444 gr. arrow: your current set-up has just under 75 lb/ft KE (540 grs. @ 250 fps). You will lose ~1% KE going to the lighter arrow. At 443 grs. that puts you right around 275 fps.

 

[Billy Goat]

My draw length is 32.5 so I shoot them uncut at 32". I would drop down in spine from the 250 to a 300, then use the factory inserts which are 14gr, and switch to a 125gr tip which should get me to total arrow weight of about 440. My current arrow is 540 and actually chrono'd at 250. Every calculator I use shows speed going to about 285 with the lighter arrow, so that seems consistent with your findings too.

I'd stay stiff.

No reason not to stay with a 250 and just go with a standard insert. Should have plenty of room to cut your current shaft past the insert and stick a standard weight insert in.

That would probably have you north of 275 fps.

 

[IrkedCitizen]

@Kbhillhunter what bow and poundage are you shooting?

 

[Kbhillhunter]

@Kbhillhunter what bow and poundage are you shooting?

60#, 32.5" DL and 350 IBO

 

[IrkedCitizen]

What chronograph do you have? 540gr @250fps from a 32.5" draw on a 60# bow that IBO 350fps doesn't seem right to me.

 

[Mighty Mouse]

What chronograph do you have? 540gr @250fps from a 32.5" draw on a 60# bow that IBO 350fps doesn't seem right to me.

Agreed. I'm guessing @Kbhillhunter is shooting a Mathews Atlas, which is (deceptively) marketed as having an IBO rating of 350 fps. IBO ratings are generally assumed to be measured at 70# draw weight and 30" draw length with a 350 gr arrow, but I believe the IBO rating protocol actually only specifies an arrow weight-to-draw weight ratio (of 5 gr per pound), not a draw length. If you read far enough down on the Atlas product page, Mathews does eventually state that their 350 fps claim is at a 34" draw length. 350 fps at 34" equates to approximately 310 fps at 30". Using 310 fps at 70#/30"/350 gr as the starting point, my calculator estimates exactly 250 fps at 60#/32.5"/540 gr.

 

[Kbhillhunter]

Agreed. I'm guessing @Kbhillhunter is shooting a Mathews Atlas, which is (deceptively) marketed as having an IBO rating of 350 fps. IBO ratings are generally assumed to be measured at 70# draw weight and 30" draw length with a 350 gr arrow, but I believe the IBO rating protocol actually only specifies an arrow weight-to-draw weight ratio (of 5 gr per pound), not a draw length. If you read far enough down on the Atlas product page, Mathews does eventually state that their 350 fps claim is at a 34" draw length. 350 fps at 34" equates to approximately 310 fps at 30". Using 310 fps at 70#/30"/350 gr as the starting point, my calculator estimates exactly 250 fps at 60#/32.5"/540 gr.

This is exactly right

 

[IrkedCitizen]

Thats why I asked what bow. 310 IBO makes more sense.

Is there a reason why you run your arrows so long? I have a 31.25" draw length and I cut my arrows to 29.25".

Personally I would cut your .250 spine carnivores to 30.5" and remove the 100gr insert for the 14gr insert. That would lighten you 14.55gr of shaft and 86gr on the insert for 100.55gr savings which would bring your arrow to 440gr. If you absolutely want to keep your arrows full length then you'll still save 86gr by switching the inserts to the stock 14gr ones making your arrows 454gr. You can always used lighter vanes to save some weight as well.


@5MilesBack I know you have a pretty long draw. What say you?