size my broadhead

[rvalleyp]

Hey guys I'm looking for help building an arrow set up for a ventum pro 30, 80lb, 29'' draw
This is what I have so far,

4mm axis arrows 250,

illuminated nocks- not sure if one brand is better than another

vanes- I've always used blazer vanes and will on new arrows unless suggested otherwise

broadhead- iron will snyder core system, I want the arrow speed 280-290 for tunability but I need help with upfront weight to get to the speed I want

 

[TreeStandAthlete]

Well you'd need to know your arrow length to get a more accurate number but assuming you cut them at 29" 200gr up front (broadhead and insert/collar combined) will get you to 289fps on the calculator. Given bow companies tend to exaggerate their listed speeds a bit you should safely be at or above 280fps with that build. If I were you I'd build it out so you have ~75gr in collar/insert and shoot some 125gr field points through a Chrono. If it's a little faster than you want you can bump up to 150gr, if it's a little slower drop to 100gr.

I use this calculator, it's usually within 10fps of what the Chrono says at the shop.

Arrow Speed Calculator

Arrow speed calculator finds the real speed of an arrow for a bow with custom parameters.

www.omnicalculator.com

Edit: forgot you said lighted nocks. That'll just mean you need to take a other 15-20 grains off the front end to keep the same speed (assuming nocturnals which weight in about 25gr if I remember correctly).


2nd edit: It brings a little sunshine to my day that you didn't list a desired FOC

 

[Mighty Mouse]

Here's the method I use to estimate speed at various arrow weights:

1. Look up the bow's advertised speed (usually rated at 70 lb DW/30" DL with a 350 gr arrow)​

2. Adjust speed rating to your DW. 2.5 fps per lb is a decent rule of thumb.​

3. Adjust DW-corrected speed from step 2 to your DL. 10 fps per inch seems to work well for bows with DL-specific cams/mods. For bows with rotating mods, 15 fps per inch may be a better estimate at DL's in the mid-to-low end of the adjustment range for a given cam.​

4. Calculate KE with a 350 gr arrow using the speed from step 3. Formula for KE (in ft-lbs) is: fps² × gr ÷ 450,240​

5. Rearrange the KE formula to solve for speed or arrow weight assuming the KE value calculated in step 4 remains constant:​

A. fps = sqrt(ft-lbs × 450,240 ÷ gr)​

B. gr = ft-lbs × 450,240 ÷ fps²​

​

For your bow and desired speed range:

1. Rated speed = 342 fps​

2. DW adjustment: 342 fps + 2.5 fps/lb × (80 lb – 70 lb) = 367 fps​

3. DL adjustment: 367 fps + 15 fps/in × (29 in – 30 in) = 352 fps​

4. KE = (352 fps)² × 350 gr ÷ 450,240 = 96.3 ft-lbs​

5. Arrow weights at the high and low end of your desired speed range:​

96.3-fps × 450,240 ÷ (290 fps)² = 516 gr​

96.3-fps × 450,240 ÷ (280 fps)² = 553 gr​

 

[Billy Goat]

For upper 280's with that bow and specs I think you probably want 520 gr taw.

Personally I'd not want 4mm and definitely no lighted nocks unless firenock. The lighted nocks all fit different than your regular nocks, so you need to tune with your lighted nocks, and I don't feel like any other than firenock are held to any tight tolerance. The 4mm's suck with component stacking, you will solve a lot of that with the Iron Will system, but I just don't see the gains for the headaches. It's a royal pia to get fletching right on those skinny shafts. They aren't helping with the wind much once you put blazers and a fixed head on the front, and your broadhead ferrule busts a hole around the size of a 22 shaft, so I just don't see the real world penetration gains.

 

[Mighty Mouse]

A 250 spine 4mm Axis cut around 28-29" with 200 gr total up front, a 25 gr lighted nock, and 3 Blazers should put you in your desired speed range with appropriate dynamic spine (according to qSpine).

I'll second @Billy Goat 's word of caution about 4mm arrows. The Snyder Core system is definitely the way to go if you choose the 4mm route, but those components won't work with any other arrow diameter if you decide to change things up in the future. A 5mm/.204" shaft with a standard thread HIT would give you some of the benefits of smaller diameter arrows (to the extent there are any) without marrying you to Deep Six components.

I'll also second the Firenock recommendation. They're expensive but far superior to any other lighted nock I've tried.

 

[TreeStandAthlete]

To tack on to the lighted nock talk. Don't rule out reflective arrow wraps. They weight less, are legal in every state (I'd imagine), and you don't have to worry about them not turning on or running out of battery. Oh and they are way cheaper. Giant downside they aren't nearly as much fun to watch fly.

 

[Laramie]

Or just use an accurate chronograph and test a few arrows... I don't trust numbers on paper... Or on a forum.

 

[rvalleyp]

Thanks for all the help, this is my plan

arrow- 284g
lighted nock- 20g
vanes- 20g
BH- 135g
collar- 25g
insert- 25g

taw 509g

using the online calculator linked that should put me real close to 290

 

[43.6N]

Hey buddy, same boat, same specs as you. I recently picked up a v3x and wanted to build some new arrows for it.

I’m 6’, 29” draw, 75lbs, 80% let off.
I built:
Black eagle rampage 300 spine: 8.7 gpi @ 27.5 inches.
Standard 52 grain steel inserts.
75 grain brass weight for extra weight and insert length (I glued the insert and the weight in as a single unit for increased bonding surface area, and to decrease my dynamic spine)
Iron will single bevel 125gr.
3 Aae max hunters.
Regular black eagle .204 nocks, listed at 10gr.

Calculated to 515, 19.8% foc, at 275 fps on gold tip calculator.
Actual measurements after the build: 521gr +\- 4 grains (glue? Individual piece tolerances?)
Measured 21% foc carbon to carbon.
289 fps +\- 2 fps at 2500 feet above sea level.

Good luck and hope my numbers help.

 

[rvalleyp]

update for anyone interested
I got my new ventum pro 30 in, it's an 80lb bow maxed out but I didn't check actual draw weight
I went with the axis 4mm with a taw of 492g I don't have the lights nocks on yet
the arrow choreographed at 291 ft/s
The online calculator above had it at 294 so very close.
My goal was to have as heavy of an arrow as I can and be around 280/290. I was able to build the arrows ahead of time with the online calculator linked above.
thanks