I recently purchased a another bow and will be building some carbon arrows for it. I use Stu-Miller spine calculator. I can use a .400 spine or .340 spine, depends on how I build them. The .400 spine arrows come out at 8.7 GPP, FOC is 16.3, speed is 197 and arrow energy is 41.3. The .340 spine are 10.9 GPP, FOC is 17.3, speed is 177 and arrow energy is 41.2. My question is with the energy close to the same, which arrow would be the better hunting arrow or would it be a wash. I know heavier is usually quieter and better for the bow. Any help would be appreciated. Chris

you'll most likely enjoy the feel of the heavier arrow.

The other reasons pale in comparison..

KE measurement provides little if any insite with regard to penetration.

FOC measurement does not even provide measureable increases until moving above 19%.
For me, appreceable visible gains have not been observed until ~25.

The much higher mass 10.9 gpp arrow should visibly provide significantly more penetration.
Your own testing results will satisfy any concerns.

I'd rather have a stiff shaft with a heavier point than weaker shaft with a light point.  I like the quietness of my bow with that arrow setup and I think the heavier head seems to fly better in windy conditions.

I would take whichever shaft would tune with a 150gr.-225gr. head, which will depend on your draw weight and the length of the arrows.

QuoteOriginally posted by Friend:
[QB] KE measurement provides little if any insite with regard to penetration.

I have tried telling folks that forever.  

God Bless,
Nathan

Update: I ordered my GT 7595 Blems from Big Jim and 5 inch feathers from Magnus all together with a 100 grain insert and 125 grain tip. Total arrow weight at 31.5 inches was 599.8 grains. Made my arrows today and shot field tips with bare shaft and they grouped together no issues there. I then screwed on a 125 grain Snuffer. At 20 yards I was consistantly hitting a 2 inch square on my target. Starting to feel real good about this set-up.

The one that fly's the best when released by you from your bow.  

Charts are great for narrowing the selection down but only you shooting a particular shaft can determine the correct choice.  Good flight will always be more important then KE, FOC, FPS, etc.