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Finding max. grain broadheads


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#1 runNgun

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Posted 26 November 2006 - 06:23 PM

I've just started looking at different broadheads and am a little stumped. How do you know what grain of broadhead to buy? Also, what do you like more mechanicals or fixed because I'm not sure what to buy. What are some good moderatly prices heads?

Thanks!
Run
-Eric

#2 McBruce

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Posted 26 November 2006 - 09:27 PM

run...alot of the stuff in archery, comes very close to the math you do in school.

sort of like an algerbra formula... it all equals out on both sides. if you change one it changes the other.

so start off with 5 grs per lbs
this means for every lb of draw weight , figure a min of 5 grs for arrow weight.
ie a 70 lb pull will require a 350 gr arrow ( 70 x 5 = 350 )

if you go lighter then this you can possibly damage your bow and you will almost certainly void any warranty you have.

Now you know your min weight of an arrow. So when you start looking at arrow shafts you can find some at 6.2 grs per inch and others at 8.1 grs per inch.

if you go with a lighter grain per inch you may need to increase your broad head weight to keep it above the 350 we figured you would need in the above set up.


Now you start getting into the fun stuff... you have FOC that you need to figure out. ( Front of Center ) the range of front of center depends on what works for you. the range is between 7%-14% . However most will say its actually between 9%-12%. So lets just call it 10% for ease of doing the math.

Front of Center is the balance of your arrow. example...take a pencil and find the center and balance it on the tip of your finger...now it will tip of. the earser end is heavier so you have to move your finger closer to that end to find the balance point ( this would be considered Front of Center )

for an arrow to fly properly you want to be about 10% ahead of Center. (FOC)
if you have a 26 inch arrow and your broadhead is another 1 1/2 inches long. your total arrow length is 27 1/2 center would be 13 3/4 inches.
10% of that would be 1 3/8 inches so your balance point would be 13 3/4 +1 3/8 and you are at 15 1/8 inches from the nock.

so now take your arrow, and put an 85 gr broad head on it and see if you balance at 15 1/8 inches if the tail drops and the tip rises you need a heavier broadhead.
move up to a 100 gr broad head...keep playing with this untill you find the proper tipped broad head. Now make sure you wiegh your arrow and see that you are over the 350 gr min.

you can adjust some of this by the type of vanes you use, and if you have bushings on the back and type of noc.

play around and you will find a set up that works for you.

now here is my set up.
a 26 inch arrow with a 100 gr broadhead on goldtip xt shafts I shoot at 67 lbs
I have a 11% front of center and my arrows weigh in around 395 grs

so why not move up to 70 lbs? because when I do, the spine of the shaft flexes to much and my groups are not as tight. to increase (or stiffen the spine ) I have to move up to a heavier arrow 75/95 instead of the 55/75 I now shoot. When I go to a heavier arrow I loose speed.

so I end up shooting heavier lbs and get a slower arrow and have almost the exact same KE as the lighter arrow with less lbs and faster speed.

I have played around with my set up and lengthed my arrows bit, gone to an 85 gr head and gotten more speed, but I am right at the edge of min arrow weight ( the 5grs per lb of draw ) and I dont feel I get the same pentration as I do with the set up I'm shooting.


SOOOO how do you come up with broad head weight.
make sure you are above mim specs and try to hit close to 10% on FOC and that is what you should use.

diffrent arrows ( diffrent weights and spines ) will effect your final result but once you come up with a combo that works for you. you'll love it :)
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#3 Rowdy Yates

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Posted 26 November 2006 - 10:13 PM

Great way to explain it Bruce.

Run fixed blade price wise run $25 for three heads and more $ and mech. heads are about the same. If your starting off I'd start with the fixed blade type and go to easton.com for how to tune your arrows flight when shooting a fixed blade. They have a great down loadable explaination of how to do it. Also goldtip.com or gold tip arrows has more info on front of center on their web site. It's fun stuff and easy to get the hang of it today thanks to all this web born info. Good luck and ask questions. ;)
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#4 Jeremiah

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Posted 27 November 2006 - 08:28 AM

See, that's why I hired Bruce here. (Taught him everything he knows. LOL)

You can cheat on a lot of that stuff with the calculators found here...
http://home.att.net/~sajackson/archery.html

Just use the "Arrow FOC & Weight" tables. The reason you will find 90% of stores these days carry tons of heads in 100 grain and not as much in lighter or heavier configurations is because a 100 grain head tends to provide ~10% FOC on a typical length carbon hunting arrow. You will usually find you need to go heavier in weight only if you are using heavy nocks (like a Lumenock), wraps or some sort of paint dip on the back end of your arrow. Lighter... Well, I'd always stay to the heavier side unless it's a youth set-up with shorter/lighter arrows that will balance differently.

A pack of 6 Muzzys will run you ~$30. I still think they're as good a value to performance balance as you'll find. I've always advocated shooting a fixed blade head if the set-up (and shooter form) permits. If you find a fixed head is flying erratic and bow tune has been exhausted then it may be time to try a mechanical. Grim Reapers and Rocky Mountain Snypers (or Rage) have proven very effective on several different types of game.

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#5 Leo

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Posted 27 November 2006 - 10:13 AM

In a nutshell Run here are some essential points to remember.

1. The weight broadhead you choose is more dependent on the arrows you have than anything else. NOT what you're hunting for. IE. you don't just need a heavier head for bigger game.

2. Go for a 10% or higher FOC with your arrows. Carbon shafts especially benefit from a higher FOC (Sometimes you need as high as 12%)

3. Bruce nailed something particularly valuable. Don't get hung up on trying to match arrows to a specific draw weight. There are not enough components available, nor do you likely have enough money to try everything and make this work. Match your draw weight to your arrows. Bow weight adjustment is free ;) A huge number of archers could improve their accuracy tremendously by just turning their bows down 2lbs. But they just can't make themselves do it because it makes them feel weak. Look at some tourney pro setups, practically none of them shoot their bows maxed out. ;)

4. If you need more FOC but don't want or can't get a heavier head. Try lighter fletchings like feathers or Blazer vanes. Or you can try a lighter nock like a Tune-A-Nock.

There are indeed more tricks you can play, but these are the main ones. Be sure to check your FOC of field points versus broadheads. Broadheads IME always have lower FOCs than the same arrow with a fieldpoint. So if you are boarderline with your fieldpoints the broadheads will be under.

FOC also plays a role in penetration efficiency. But that's for another post :)
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#6 mudduck

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Posted 27 November 2006 - 10:20 AM

Following the above advice should get you the right arrow and proper size broadhead. One thing you should get to help you tune your broadheads is an arrow roller/spin check. After you attach your broadheads, and to ensure proper flight, you must make sure that your broadhead is in exact alignment with your arrow. I have found that the best way to do this is with an arrow roller/spin check. Just place arrow with broadhead on it and roll the arrow,watching the tip. If any wobble occurs, then simply apply pressue to tip to straighten. Proper alignment is critical for proper flight. Posted Image

#7 runNgun

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Posted 27 November 2006 - 04:39 PM

Thanks for all the replies everyone! I have 6 arrows with field tips on them, so your saying that it is advisable to get new arrows for broadheads instead of just taking the field tips off and installing boradheads on them?
-Eric

#8 mudduck

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Posted 27 November 2006 - 05:13 PM

You can use the same arrows, but most will have a set for practice and a set for hunting. Use the same weight Broadhead as your field points. IF you are having good flight with your present set-up, then there should be little if any problems.

#9 McBruce

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Posted 27 November 2006 - 11:22 PM

Run:
I spent 12 years shooting, and just depending on the guys at the archery shop to give me what I needed. NO ONE ever explained all this type of stuff to me, untill I Joined the old site. It was awesome how so many people helped out and explained all this to me.
Jer is right he taught me a lot. You should see some of the emails he took the time to write and send when I was asking all these same type of questions.
Leo is another one who helped out alot. I had cranked my bow up to 70 lbs and my groups opened way up. he asked a number of questions and said my arrows were under spinned and I was getting to much flex on the shot.
according to the charts I should have been fine...but when I turned my bow back down to 67 lbs ( a whole 3 lbs less) My groups tightened right back up. No doubt it was the arrow spine causing it.
Now be careful when Robert starts giving ya advise. he had me floating arrows in the bath tub ones... what he was showing made sense but I'm not so sure he wasn't pulling my leg just a bit :)
Ohhh and he even got me to build up a whole set of Plunger arrows .....:)

hope all this stuff helped out.
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#10 runNgun

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Posted 29 June 2007 - 11:29 PM

I know this is a pretty old topic but I was wondering if you guys could help me again. I'm really having a tough time figuring all of this stuff out.

I have the arrow weight I need I think. 40# x 5 = 200 grains. Am I right on that?


My arrows are 27.5 inches with field point and nock and if I'm getting this I take that by either 6.2 or 8.1 per inch for arrow shaft which comes out to 170.5 grains when I take it by 6.2 and 222.75 grains with 8.1 . Is that the weight of the arrow without the broadhead?

so since I have the same length of arrow that bruce made an example of in his first post, would I be 15 1/8 inches from the nock too?


back to my arrows....... if I bought arrows that were 6.2 grains per inch and put 85 or even 100 grain broadheads would I be okay?


I'm shooting 40#'s right now but hope to be 50-55#'s by the time I can bow hunt my myself when I will get out for real.

I guess I'm just not getting where the draw weight comes into play with the FOC and everything else.


If this can get me on track a little better, here are some specs:

40# draw weight

26" draw length

27.5" arrows with field tips and nocks

(3) 2 inch blazer vanes

Carbon Express Terminator 4560 carbon arrows (though I will be getting seperate arrows for hunting ONLY)



Thanks for any help you can give me. I am completly stumped :doh: :blink: :worry:



THANK YOU!!!!
-Eric

#11 Leo

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Posted 30 June 2007 - 01:34 PM

200grains would be your minimum IBO TOTAL arrow weight. Your arrows can be heavier and still be fine. You just don't want to ever shoot an arrow that weighs less than that.

Grains per Inch specs on arrows are for the shaft material only. It does not include the weight of nocks, fletchings, inserts or heads. The best weigh to figure out your total arrow weight is simply to weigh them. Adding up spec weights of components is guaranteed to be only a rough estimate.

Likewise with FOC. Actually measure it. The programs that suggest FOC from components aren't all that accurate. These programs are useful if you are going to make a change in components later. They help you decide if the component change will do what you want.

FOC comes into play with Draw weight because FOC effects the spine of the arrow. The more FOC the less spine.

For CE4560s 100grains is probably as light as you want to go. You can shoot the 85s the arrows will be faster but your groups will suffer.
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#12 runNgun

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Posted 30 June 2007 - 03:53 PM

200grains would be your minimum IBO TOTAL arrow weight. Your arrows can be heavier and still be fine. You just don't want to ever shoot an arrow that weighs less than that.

Grains per Inch specs on arrows are for the shaft material only. It does not include the weight of nocks, fletchings, inserts or heads. The best weigh to figure out your total arrow weight is simply to weigh them. Adding up spec weights of components is guaranteed to be only a rough estimate.

Likewise with FOC. Actually measure it. The programs that suggest FOC from components aren't all that accurate. These programs are useful if you are going to make a change in components later. They help you decide if the component change will do what you want.

FOC comes into play with Draw weight because FOC effects the spine of the arrow. The more FOC the less spine.

For CE4560s 100grains is probably as light as you want to go. You can shoot the 85s the arrows will be faster but your groups will suffer.



Thanks Leo! So for my arrows, would about 125 grain broadheads for the best? Since you told me what about the best weight of broadhead is do I still need to figure out the FOC?
-Eric

#13 Leo

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Posted 02 July 2007 - 07:05 PM

The 100s will be fine. As will the 125s. I can't tell you for sure which will behave best at your poundage.
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#14 runNgun

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Posted 02 July 2007 - 09:15 PM

Thanks a lot Leo! I will try to test both 100 grain and 125 grains.
-Eric




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