some one help me with a spine calculator...

[DanielB89]

I have a Black Widow MAIII I am trying to change up arrows and have read how people use a spine calculator find out a compatible arrow.

My bow is #53@28, i draw to 28.5.  
I am currently shooting Beman MFX .340's cut to 30.5.

[damascusdave]

I for one need a lot more information before I am even going to try to help you

DDave

[DanielB89]

Dave, whatever you need tell me.
Arrows are .340 spine beman MFX's cut to 30.5".
I draw to 28.5. Standard HIT inserts.

3 fletch 5" feathers.

[dbd870]

Point weight?

[Bud B.]

Type string? What gpp you looking for? FOC? Like dbd870 asked, what point weight are you using now and what would you like to use on the new arrows?

Based just on what you've given you could go with a 7595 GT Trad with a 100gr insert and 125 points and be close, but that'd give you nearly 11gpp.

A 55/75 with standard insert and 125 would be close but give you just over 8gpp.

It's a crap shoot unless you can give all the variables needed to enter into the calc spreadsheet.

Strike plate thickness is also needed. How far to center or past center is the MAIII? Do you use arrow wraps?

[Bud B.]

And you could also check with Black Widow if you haven't already. They may have the best insight of all.

[Bladepeek]

If those .340s are flying really well for you, you can plug in all the info in Stu's calculator. Make sure you get the cut-to-center measurement right and all the other specs correct. Then, you can adjust the "personal form factor" +15 to-15 until the bow rating matches the arrow's dynamic rating.

After that, without changing any of the bow info, you can plug in what ever arrow you like and play with the point weight, insert weight and length to get the same dynamic arrow reading.

Everyone uses the calculator differently (or not at all!), but for me its greatest value is to put me fairly close on a totally new bow. Then I fine tune the bow/arrow combination until I feel the arrow is flying perfectly. Put all that info into the calculator and I have a bench mark. Then I can play "what if" all day long and know that the combination I decide to try next will be pretty much dead on.

[DanielB89]

I  not sure how far past center it is cut. The MAIII was not an option on the calculator I tried, so I just used the PMA.

Beman MFX .340's
30.5" long
175 grain head
Standard insert
3 5" feathers

I  wanting to drop weight but keep the same point weight. These arrows are 10.4 gpi and I could like to be closer to 9gpp than over 10.

[damascusdave]

My buddy Cameron I have pretty much come to the same conclusion...drop the carbons and switch back to aluminum, or if you want small diameter Full Metal Jackets...just a lot easier to deal with in the long run

DDave

[riverrat 2]

Daniel,I agree with the above post by DDave. If you get a chance try some luminum'. I love the he-Double hockey sticks out of mine bud.  rat'

[Bladepeek]

DanielB89, I show those arrows being just a little weak for your bow, but if they are flying well, a personal form factor of -11 will show them matched to your bow. Then you can plug in GT7595 (9GPP)
Easton ST Excel 340 (9.3GPP)
Easton Axis FMJ 340 (10.3GPP)
or whatever strikes your fancy and see how the weight compares.

[DanielB89]

Originally posted by Bladepeek:
DanielB89, I show those arrows being just a little weak for your bow, but if they are flying well, a personal form factor of -11 will show them matched to your bow. Then you can plug in GT7595 (9GPP)
Easton ST Excel 340 (9.3GPP)
Easton Axis FMJ 340 (10.3GPP)
or whatever strikes your fancy and see how the weight compares.

What does a form factor of .11 mean? lol

Thanks for all the help guys!

I would drop all the carbons if i didn't have over 3 dozen. lol  I a set on arrows for a while, i just want to do something a little different.  Thinking that dropping about 75 grains would help with trajectory.

[Bladepeek]

Daniel, that's a "minus 11". It will change the apparent draw weight down quite a bit. That's if the current arrows are really flying well and you are happy with the tune. That will allow you to show bow weight and dynamic spine of the arrow as being the same. Then you just need to plug in different arrow combinations to get that same dynamic spine and they should be tuned about the same as your current arrows.

[DanielB89]

ok.  So that is saying that my release is actually slowing down the arrow a good bit?  

Just making sure i understand.

[Bladepeek]

You said that - I didn't. All I was saying is that if you are really happy with the current set up, you can duplicate that flight with a lot of different arrows/lengths/point weights by just setting up the hypothetical arrow to match the dynamic spine of your current set up.

You may well be right about your release slowing thngs down. I suspect mine is. But, I wouldn't worry too much about what the calculator says about your bow setup. I was just giving you a way to copy the tuning set up you currently have with different arrows. You might want to try some 145 gr field points on your current arrows and if they also fly well, I'd guess Stu's calculator might be right in the arrows being slightly weak. If the 145s don't fly as well as your 175s, then you know you will want to stay with the heavier point and adjust the calculator to match what you are seeing. Points are so cheap it's the easiest way to change things without cutting shafts, or making other changes.

[DanielB89]

bladepeek,
thank you for all your help!  

I will try bare shaft tuning the arrows again and see how they turn out.  I honestly never paper tuned these arrows, i just assumed they were good because of the last arrows i tuned.  

I have some beman ICS bowhunters .340's that i bare shaft tuned and they flew like darts.  A friend of mine traded me these .340's and they are a little skinnier shafts than the bowhunters.  

Would the shaft being a little skinnier, would that make a big difference?

[Bladepeek]

I would think, being the same spine, but skinnier and therefor closer to center, they would be even more tolerant of small differences. It's all fun, right?

[Orion]

Daniel:  I'm a bit surprised that the .340s aren't a little stiff, particularly if you don't have much weight up front.  If you reduce the front end weight on the .340s, I think they will likely become too stiff.

You could also drop arrow weight by going to .400 spine Axis or ICS shafts. The shaft itself will be about 16 grains lighter.  May need to shorten the shaft by an inch (9-10 grains) if you use the same inserts, adaptors and heads you're currently using on your .340s, but I expect you'll want to (may have to) lighten up one or more of those components as well to achieve a lower overall arrow weight. For what it's worth, I think you're already shooting a good arrow weight at 10.4 gpp. Good luck.

[DanielB89]

Thank you for the replies.

I have read several times about how these arrows should be too stiff. Mentally, I agree, but during tuning, I don't agree. Lol.

I have a sage sammick I'm trying to set up for a friend. It's #45 and I immediately thought the 35/55's would work out. Ordered a dozen, took one out for bare shaft tuning, cut it all the way down to my draw weight and could not get it to stop showing weak. Swapped to a 5575 and at 30" with a 125 grain tip, it stiff shows weak.

I honestly do not know why all my bows tune stiff. I often wonder if it's my release, but wouldn't a sloppy release make the arrows show stiffer?

[Bud B.]

Have you shot some fletched arrows?