Arrow Setup - Elk

[BrockWinegar]

Hey all looking for advice on my elk arrow options. Have 30” Easton Sonic 6.0 250 spine with sevr 1.5 hybrids. Shooting 76 lbs, 32.5” DL.

1. 488 gr, 13.8% foc, 295 fps
2. 499 gr, 12.4% foc, 292 fps
3. 513 gr, 15.3% foc, 286 fps

Option 2 has a lighted nock, worried 3 could be underspined.

Hunting elk in N Washington, likely shorter shots in/around brush. Not going to change arrows or broadheads so mostly looking for opinions on those 3 options. I know I’m splitting hairs here a bit but since I have the option want to pick the best one!

Thanks!

 

[Turkeygetpwnd38]

Whichever shoots the best

 

[roosiebull]

It won’t matter even a little bit, as long as they shoot well, you have a lot of surplus energy

 

[S.Clancy]

I would shoot the lowest FOC arrow, you've got to be right on the edge of being under-spined with a 32.5" draw and 76 lbs.

 

[Beendare]

You won't see a lick of difference between the first 2 options ....and be hard pressed to tell the 3rd at 40y and in.

I would usually opt for the heavier arrow but it is possible you are getting close to under spined with #3.

 

[Bump79]

I would shoot the lowest FOC arrow, you've got to be right on the edge of being under-spined with a 32.5" draw and 76 lbs.

I agree with this. I would go option 2 or move to a 200 spine. Even a 175.

Honestly, I'd probably just cut some draw weight out to 70#. At 32.5" draw you don't "need" more it is always nice. I get pass throughs consistently with 70# 30". If not, for your specs I'd go stiffer than 250. A mechanical benefits from a stiffer arrow as well.

@BrockWinegar The speeds you mention don't quite make sense to me. Are these estimated or with a chrono? Some online calculators are junk, especially at your draw. So I made one that is based on a large chronographed dataset. I'd be very interested to see how it compares at this long draw.

Arrow Speed, KE and Momentum Calculator — The Arrow Builder

Many online arrow/bow speed calculators use an oversimplified calculation to determine arrow launch velocity. This results in inaccurate results, especially at higher grain weights. Increasing arrow mass always will lead to marginal increases in KE, meaning the bow gets more efficient as grain wei

www.thearrowbuilder.com

 

[S.Clancy]

@BrockWinegar The speeds you mention don't quite make sense to me. Are these estimated or with a chrono? Some online calculators are junk, especially at your draw. So I made one that is based on a large chronographed dataset. I'd be very interested to see how it compares at this long draw.

Arrow Speed, KE and Momentum Calculator — The Arrow Builder

Many online arrow/bow speed calculators use an oversimplified calculation to determine arrow launch velocity. This results in inaccurate results, especially at higher grain weights. Increasing arrow mass always will lead to marginal increases in KE, meaning the bow gets more efficient as grain wei

www.thearrowbuilder.com

Same, I'm shooting a similar weight arrow, with slightly higher poundage (80) but 4" less draw length (28.5" vs 32.5") and getting low 280s. He should be over 300 fps easily

 

[BrockWinegar]

I agree with this. I would go option 2 or move to a 200 spine. Even a 175.

Honestly, I'd probably just cut some draw weight out to 70#. At 32.5" draw you don't "need" more it is always nice. I get pass throughs consistently with 70# 30". If not, for your specs I'd go stiffer than 250. A mechanical benefits from a stiffer arrow as well.

@BrockWinegar The speeds you mention don't quite make sense to me. Are these estimated or with a chrono? Some online calculators are junk, especially at your draw. So I made one that is based on a large chronographed dataset. I'd be very interested to see how it compares at this long draw.

Arrow Speed, KE and Momentum Calculator — The Arrow Builder

Many online arrow/bow speed calculators use an oversimplified calculation to determine arrow launch velocity. This results in inaccurate results, especially at higher grain weights. Increasing arrow mass always will lead to marginal increases in KE, meaning the bow gets more efficient as grain wei

www.thearrowbuilder.com

These are based on my chronoed 3D arrows and adjusted at 3fps/10gr. So yes estimates but based on a chronoed arrow. Ill build some out and update this threads with actual chrono speeds.

 

[Hussar]

All three of those will shoot just fine. Personally, I'd shoot the 488 grain arrow. The extra speed will give you some forgiveness and they're all plenty heavy enough to kill anything in North America.

I'm also confused with the speeds unless OP is shooting an older, slower bow. My bow setup is a V3X 33, 77.6 lbs @ 28.625" draw length. I'm shooting a 488 grain arrow at 284 fps according to my chronograph.

 

[BrockWinegar]

All three of those will shoot just fine. Personally, I'd shoot the 488 grain arrow. The extra speed will give you some forgiveness and they're all plenty heavy enough to kill anything in North America.

I'm also confused with the speeds unless OP is shooting an older, slower bow. My bow setup is a V3X 33, 77.6 lbs @ 28.625" draw length. I'm shooting a 488 grain arrow at 284 fps according to my chronograph.

I’m second guessing this now too. Shooting the Lift XD. But I chronoed my 3D arrows weighing 434 gr at 311 fps. Personally weighed and chronoed so not sure the discrepancy. Have not verified 76 lb draw, have the 75 lb 80% mods in and limb bolts are all the way tightened, and added 2 twists to each cable for timing. So there are some assumptions but I’d say they are pretty based.

 

[Bump79]

Personally, I like to be below 295 fps. Broadhead planeing and drag is related to velocity squared time surface area and time. Or something like that. So roughly every millisecond there will be 7% more force applied that makes flight more rowdy. So the slower one easily could be more than 10% more "forgiving".

I'm a simple engineer though... not a real smart one. But it's something like this.

All three of those will shoot just fine. Personally, I'd shoot the 488 grain arrow. The extra speed will give you some forgiveness and they're all plenty heavy enough to kill anything in North America.

I'm also confused with the speeds unless OP is shooting an older, slower bow. My bow setup is a V3X 33, 77.6 lbs @ 28.625" draw length. I'm shooting a 488 grain arrow at 284 fps according to my chronograph.

Spot on with my calcs.


@BrockWinegar with the 488 grain arrow I'd think you'll be pushing 305 fps unless your bow is very slow.

 

[Bump79]

I’m second guessing this now too. Shooting the Lift XD. But I chronoed my 3D arrows weighing 434 gr at 311 fps. Personally weighed and chronoed so not sure the discrepancy. Have not verified 76 lb draw, have the 75 lb 80% mods in and limb bolts are all the way tightened, and added 2 twists to each cable for timing. So there are some assumptions but I’d say they are pretty based.

So what I did with this calculator is make it so it's basing the velocities on KE, not random numbers. KE increases with arrow mass, draw length and weight.

So with the Lift XD being advertised weird this really helps. My IBO isn't for long draw so I just put 320. At the end of the day we're looking for KE. You can calibrate it to the speed with the 434 grain arrow and it gives us a KE 91.1 ft-lbs. Then use the slider for weight to play around with how fast a heavier one will go.
3d arrow settings


488 grain arrow. I figure 294 fps but honestly my dataset didn't have behemoths like you in it


Podium got @ 303 fps at 450 grain 32" 71#.

Sorry if it seems like I'm plugging a product here... but I don't make any money off this calculator. It's just because all the other calculators were junk and I couldn't make any predictions. So I just made it and put it out.

If I calibrate to MFJJ's numbers I get 303 fps at 488 grains. Which I think is more accurate.

 

[BrockWinegar]

Personally, I like to be below 295 fps. Broadhead planeing and drag is related to velocity squared time surface area and time. Or something like that. So roughly every millisecond there will be 7% more force applied that makes flight more rowdy. So the slower one easily could be more than 10% more "forgiving".

I'm a simple engineer though... not a real smart one. But it's something like this.
View attachment 910473

Spot on with my calcs.
View attachment 910469

@BrockWinegar with the 488 grain arrow I'd think you'll be pushing 305 fps unless your bow is very slow.

View attachment 910470

As an engineer myself, I appreciate the math and reasoning. Mathews posts a 363 ibo for Lift XD at 33.5” so a true ibo of 328 fps at 30”. And I put my weight at 75lb, maybe my twists just took out string stretch. And it came out to 299 FPS, only 4 fps from the speed I initially predicted. That’s within margin of error I would say, my estimate was likely just conservative.

 

[Bump79]

As an engineer myself, I appreciate the math and reasoning. Mathews posts a 363 ibo for Lift XD at 33.5” so a true ibo of 328 fps at 30”. And I put my weight at 75lb, maybe my twists just took out string stretch. And it came out to 299 FPS, only 4 fps from the speed I initially predicted. That’s within margin of error I would say, my estimate was likely just conservative.

Only one way to really know! Hell of a setup.

 

[BrockWinegar]

I would shoot the lowest FOC arrow, you've got to be right on the edge of being under-spined with a 32.5" draw and 76 lbs.

Agreed. It really depends on what spine chart I use, will be finding some 200’s next year

 

[S.Clancy]

Agreed. It really depends on what spine chart I use, will be finding some 200’s next year

My bet is you find more consistency with a stiffer arrow. I specifically add weight to the back of my arrow to decrease FOC so I can still shoot 300 spine @ 80lbs and 28.5" draw, 27" arrows.

 

[BrockWinegar]

My bet is you find more consistency with a stiffer arrow. I specifically add weight to the back of my arrow to decrease FOC so I can still shoot 300 spine @ 80lbs and 28.5" draw, 27" arrows.

Does adding weight to the back affect dynamic spine? I assumed any added weight to the back didn’t effect spine, just FOC

 

[S.Clancy]

Does adding weight to the back affect dynamic spine? I assumed any added weight to the back didn’t effect spine, just FOC

It stiffens the arrow.

If you want to think about it from an engineering standpoint increasing mass at the back of the arrow (or decreasing mass at the front) changes the center of mass, moving it closer to the point at which the bowstring exerts force (the nock). The decrease in distance causes the arrow to act "stiffer" at the shot

 

[BrockWinegar]

It stiffens the arrow.

If you want to think about it from an engineering standpoint increasing mass at the back of the arrow (or decreasing mass at the front) changes the center of mass, moving it closer to the point at which the bowstring exerts force (the nock). The decrease in distance causes the arrow to act "stiffer" at the shot

That makes sense, thank you!