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Hey guys looking for some help, I’m looking to go to a heavier foc on my arrows for better penetration I just bought a set of Easton fmj, and not sure what weight broadheads and practice tips I should get I shoot a Barnett terrain any help would be much appreciated
 

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I’m looking to go to a heavier foc on my arrows for better penetration
I am not completely sold on that idea.
The average crossbow arrow is much shorter and stiffer than one for a vertical bow. The penetration problem of the latter is caused by longitudinal oscillations on impact, that could be reduced by putting more mass upfront.
Heavier arrows will keep more momentum over distance, though.
You can try heavier brass inserts, and perhaps experiment with different broadhead weights. I use 100gn inserts for one of my (vertical) compound bow setups.
 

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From what I understand, FOC over 20% is what you're looking for, Grey.
This is a simple calculator for that metric. Arrow Front of Center (FOC) Calculator
There are more accurate ways to calculate that, but that might get you headed in the right direction.
A lot of the information on high FOC that I have gotten and used has been for verticals. I'm not sure how that translates to xbow application. There's sure guys here that can give you some great input. I'm in for the answers as well.
 

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Thanks guys I appreciate the info I’m not sure of it yet but still searching I was looking at GrizzlyStik and was searching through and, well ordered some 150g practice tips and see how that plays out
 

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Grey... I took more of a brute force approach to finding what worked best with my bow (Barnett Wildcat C5). I started with 20" Spynal Tapp (Zombie Slayer carbon) from South Shore Archery with 100 gr insert, spine indexed and .001 straight. This shaft is about 9.1 gr per inch with stiffness of ~ 8.5 NM^2. I use a 36 gr Launchpad lighted nock. I bought a set (6) of weighted points from 85 grains - 315 grains (85,100,150,200,250,315) I think? Shot all six on same arrow at 25 yards. 200 gr was lightest that hit target dead straight. Ordered 19" (increased spine stiffness) Spynal Tapps with 200 grain SS (instead of brass) inserts. With 125 gr BH, I have a 325 grain front end for FOC > 22% and total arrow weight of 570 grains. Put down 1/2 dozen neighborhood garden raiders last season. I rely on 1 1/2" 3-blade Ramcat BH's for good trails and quick recovery.
 

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Grey... I took more of a brute force approach to finding what worked best with my bow (Barnett Wildcat C5). I started with 20" Spynal Tapp (Zombie Slayer carbon) from South Shore Archery with 100 gr insert, spine indexed and .001 straight. This shaft is about 9.1 gr per inch with stiffness of ~ 8.5 NM^2. I use a 36 gr Launchpad lighted nock. I bought a set (6) of weighted points from 85 grains - 315 grains (85,100,150,200,250,315) I think? Shot all six on same arrow at 25 yards. 200 gr was lightest that hit target dead straight. Ordered 19" (increased spine stiffness) Spynal Tapps with 200 grain SS (instead of brass) inserts. With 125 gr BH, I have a 325 grain front end for FOC > 22% and total arrow weight of 570 grains. Put down 1/2 dozen neighborhood garden raiders last season. I rely on 1 1/2" 3-blade Ramcat BH's for good trails and quick recovery.
+1
 

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Alright I just calculated my foc with my Easton fmj and a 125g Broadhead and it’s a 9.99 I’ve got 150g practice tips coming, how much should I go to get my foc to around 20
 

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Alright I just calculated my foc with my Easton fmj and a 125g Broadhead and it’s a 9.99 I’ve got 150g practice tips coming, how much should I go to get my foc to around 20
Hi Grey... Looked up Easton FMJ crossbow arrow and found a 13.7 gr/in shaft. That's a pretty heavy (and slow) arrow for a 140 lb bow. We can address that later. I don't know what procedure you used for FOC, but using your ~10% number and matching the lever arms about the balance point with only a 1.5% difference suggests that the shafts had a 90 grain insert and no broadhead. If you include a 125 gr BH, 1 1/2" long, that adds 125*X in-gr to the right arm which must be balanced by 13.7*((21.5-x)/2) in-gr on the left. X=1.12 forward added to the 2.15 inches to start gives roughly 3.27 inches forward of center or ~ 15% FOC. NOTE: Math and logic subject to correction.:unsure:

On the heavy arrow issue. I use a 1/3 lighter arrow shaft and put 325 grains in the front end with a 200 gr insert and 125 gr BH. This gives me a FOC of roughly 22% in spite of a 36 gr lighted nock. A 9.1 gr/inch Black Eagle Zombie Slayer will easily handle your 140# draw.
 

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Grey if you want to go down the rabbit hole on building good FOC arrows, go to YouTube and look for Ranch Fairy vids on the process. He's a good source of information although he's using vertical equipment. Or look up Dr Ed Ashby foundation and start reading. It's good stuff and definitely gets you to thinking/questioning everything you've been taught.
 

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go to YouTube and look for Ranch Fairy vids on the process. He's a good source of information although he's using vertical equipment. Or look up Dr Ed Ashby foundation and start reading.
Bofos... I don't think Troy is going to take up crossbow activities any time soon, but a lot of his "hog research" with vertical tackle carries over. The process I used in post #5 (above) is taken almost directly from some of his work to find the "sweet spot" for a setup with minimum lateral waving of the arrow on impact. If your arrow is not "dead straight" when it hits the target, you are losing "penetration energy" of the broadhead.
 

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Gingerjake - yes sir I figured your information came form that type of process. I would think that the process would work just as well for xbow application. I'm new to xbow this year so I'm working through this now. Thanks for your input!

Sent from my SAMSUNG-SM-G930A using Tapatalk
 

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Hi Grey... Looked up Easton FMJ crossbow arrow and found a 13.7 gr/in shaft. That's a pretty heavy (and slow) arrow for a 140 lb bow. We can address that later. I don't know what procedure you used for FOC, but using your ~10% number and matching the lever arms about the balance point with only a 1.5% difference suggests that the shafts had a 90 grain insert and no broadhead. If you include a 125 gr BH, 1 1/2" long, that adds 125*X in-gr to the right arm which must be balanced by 13.7*((21.5-x)/2) in-gr on the left. X=1.12 forward added to the 2.15 inches to start gives roughly 3.27 inches forward of center or ~ 15% FOC. NOTE: Math and logic subject to correction.:unsure:

On the heavy arrow issue. I use a 1/3 lighter arrow shaft and put 325 grains in the front end with a 200 gr insert and 125 gr BH. This gives me a FOC of roughly 22% in spite of a 36 gr lighted nock. A 9.1 gr/inch Black Eagle Zombie Slayer will easily handle your 140# draw.
Sorry for the late response, but with the eastons would that be a problem doing what I’m wanting to do a heavier foc for better penetration
 

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Sorry for the late response, but with the eastons would that be a problem doing what I’m wanting to do a heavier foc for better penetration
I went through a similar process balancing increased FOC against loss of velocity as the total arrow weight increased. A heavy shaft spreads the weight over the entire length of the arrow instead of concentrating it at the tip for increased FOC. The difference between 13.7 gr/in FMJ and 9.1 gr/in (Zombie Slayer) is 4.6 gr/in or a total of 4.6x20=92 grains that I can put in my tip to increase FOC without further slowing my arrow, but your arrow has that 92 grains spread evenly over its whole length and not helping your FOC at all. The process noted in Post #5 included running the same arrow with each of the weighted tips through the chronograph and plotting initial velocity as a function of increasing weight of the arrow. I don't have the equation at hand, but suffice it to say for MY bow going from a 380 gr arrow at 324 fps (FOC~8.5%) to a 570 gr arrow (FOC~22%), I lost ~50 fps in initial velocity. The draw weight of my bow is only 10# greater than yours, so your velocity loss as you increase total arrow weight may be comparable. If you are going to estimate FOC for a "virtual" arrow, be sure you know the weight and size of each component (nock, vanes, wrap, shaft, insert, and tip. I think Easton has a very good calculator for imaginary arrow FOC on their website. Let me know if this stuff makes sense in your build.
 
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