# Broadhead tuning. FOC% inside.



## turbo sol (Mar 13, 2011)

I've been shooting my new bow for almost 1.5 years now and have become pretty acurate. I shoot 20-70 yards pretty often and feel good about my groups and accuracy. I recently started shooting broadheads and have been running into some issues. (I should be shooting better with them IMO)

I looked into "broadhead" tuning, and the only concrete info I found was about the FOC% (front of center)

I know my shafts are short, but still clear my rest (even with my broadheads) so I thought I was ok.

I deciced to figure out what my FOC% is. and this is what I came up with based on the following equation:








http://www.redhawk-archery.com/bh-tuning.php
FOC = Front of Center
The length of the point does NOT figure into the FOC. The Easton Tuning Guide on p32 specifically emphasizes this. Easton does suggest that a 10-15% FOC is best for broadhead tipped arrows. Even more for arrows shorter than 26-27 inches.

Bowtech assassin, 68#
trophy ridge revolution rest
vanes: 2" blazers
broadhead: g5 montec 100 grain
arrow:cabelas carbon hunter 340
length from inside nock to end of insert: 27.8125
balance center of finished arrow (including tip) 17.125

by my calculations I have a *FOC of 11.57%
*
The site suggest 10-15% (more for 26-27 or shorter shafts)


I guestimated a longer shaft FOC based on my ealier measurements

Length: 29
Balance: ~18
FOC%: 12%

Length: 30
Balance: ~19
FOC%: 13.3%

Length: 31
Balance: ~20
FOC%: 14.5%

Length: 32
Balance: ~21
FOC%: 15.62%


I could also increase my broadhead to 125 grain. and maybe get a balance point of 17.625"
which would put me at a *FOC 13.37%* with my current shaft length.

along with the new 125grain tip. I could also go with 4" vane to help stablize the arrow.

What would your guys' professional opinions be on how I could get a better broad flight. (I'm paper tuned too…)


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## Dogz (Feb 15, 2010)

Your set up is very very close to mine. except that I use carbon express mayhems 27" rest is a ripcord. FOC of 11 something. I had no problem braodhead tuning. I followed these instruction http://www.archerytalk.com/vb/showthread.php?t=539460 by Doc. now my fieldpoints and broadheads are hiting in the same place.


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## bbjavelina (Jan 30, 2005)

Increased FOC can help with a number of issues. Things like ease of tuning, shooting in the wind, increased penetration. Personnally, I'm more comfortable being at 18% or more. I have hunted one season with 100 gr. heads, but doubt that I will again. For me, it needs to be at least 125 and I really like 150's. 

Just to make sure that you are aware of it, I want to metnion that -- in general -- three feathers weigh about the same as one vane. You could probably go with 3 or 4 inch feathers, maybe increase arrow control, and not lower your FOC. Obviously, decreasing weight at the rear increases you FOC. If you use wraps you can usually make them a little shorter. Lighted nocks decrease FOC. 

Many say that high FOC causes arrows to nose-dive. That has not been my experience.

In short, I'd guess that heavier points and lighter fletch would go a long way to helping your situation.

Best of luck to you.


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## nomad11 (Apr 14, 2006)

Sry but it was never defined why FOC brought you to this point as alluded to in the OP. I'm curious as to why FOC was the ultimate variable or determing factor. That said, I did not see work on tuning broadhead, inserts and shafts. Marrying all three are a BIG key to getting BH to do what your field points do. Lately I'm wondering how arrow spine is a factor......after having gone through BH, insert, shaft tuning with several arrows not performing well. This is even after rotating arrow nocks where a couple of arrows went from garbage to NICE after changing overall noc,k/shaft diameter X number of degrees. In short....why is FOC the ultimate variable when marriage of shaft/insert/BH and possibly spine are, themselves, huge influences on where an BH tipped arrow hits??


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## Ches (Aug 3, 2009)

I think nomad11 is on the right track. You did not say what your BH's were doing, only that you didn't shoot them as well or you should be shooting them better. I am one that always uses an ASD on my shafts prior to building then after insert is installed and run about 15% FOC. However, your arrows might just be fine the way they are now. Do your BH's hit left, right, up or down of your FP's? Or do they in general not group the same? I always start out by walk back tuning and move as far back as I can hold a group (60 yrds). I then use BH's and shoot them as well as FP's starting at 20 and move back to 60 adjusting my rest at each 10 yard increment. My view is that walk back with FP's sets horizontal and walk back with fp's and BH's sets both horizontal and vertical. If you decide to do this, make sure your adjustments are very, very small. A little bit goes a long way. FYI, if you get your BH's and FP's to hit andt 20 and then move back to 30 or 40 which require adjustment, your 20 will still be good, you are just fine tuning what you could not see at 20. Good luck.

Ches.


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## Learn2turn (May 16, 2011)

I have been told that magic starts to happen at 15% FOC.
And I really trust the source, so would many others here.


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## turbo sol (Mar 13, 2011)

im at 13.8% now with 125 grain heads.

I plan on shooting some over the next couple days to see what happens. hopefully that combines with a bit of broadtuning (rest compensation) I should be ok.


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## turbo sol (Mar 13, 2011)

i went out and shot some more tonight…*nothing earth shattering. I'm wondering if the issue is more in my arrow selection/construction.

I shoot Cabelas Carbon hunters 340 (65-80#)
length 27.8125
2" blazers


my draw length is between around 29"

I think I'm just going to go to the proshop, as I'm running in circles with this..


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## sarcasmn (May 2, 2012)

First and foremost I would say make sure your bow itself is well tuned. Arrows with field tips are much more forgiving than broadheads. As I learned to tune my bow better I noticed that my broadhead tuning was easier. I also spin test my arrows and broadheads before I try to tune them.


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## Ches (Aug 3, 2009)

Turbo Sol
I have read this a few times now, and I don't see your explanation of what the broadheads are doing other than "they should be shooting better". What are they doing, is it a general larger group or are they impacting in a gereral different direction than your FP's?


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## turbo sol (Mar 13, 2011)

the more I mess with this the more I think its the rest. I have already gone through 1 trophy ridge revolution. (the rotating axle got bent.) and now I see the same thing happening again. When I get the rest installed (at Bass pro) it shoots bullet holes. but over time the rest makes more and more contact. 

Ches. My arrows are irradic. 

I think its time for a different rest.


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## RatherBeInATree (Jun 18, 2012)

If you think its the rest, have you checked the level of your arrow in the rest to see if it is in fact bent? I wouldnt just eye ball it and spend money on a new rest because last time thats what happened to you. Also, just do a mental check of your form and see if you might be leaving something out or changed something. Sometimes its the operators fault and not the tool. I hope you get this figured out as I know things like this are very irratating!


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## turbo sol (Mar 13, 2011)

I finally changed rest today. The revolution was giving me a ton of issues. and if its not working right it EATS fletchings. I now have the ripcord code red installed and paper tuned today > and am expecting better results.

as for my arrows I also changed them out per my local pro shop recommendation. I am now shooting goldtip XThunter 5575 with 100grain tips.

your right RatherBeInaTree I need to be vary focused on my form as my left grip is getting in my way a bit. (as revealed by the pro shop staff.)


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