Arrow spine selection

[MT. CAT]

I got a new bow last year and just kept on using the arrows I already had (340 spine with a 100 grain tip) But with an elk tag in my pocket this year I wanted to get a better arrow set up and ready to go by September i.e. heavier arrow. heavier broadhead, higher foc. I will be shooting Gold Tip Hunter XT's. My dilemma is what spine to shoot with a 150 grain broadhead. My dl is 28.5, dw is 70lb. My arrows now are cut 28.5" from carbon to carbon. Using Gold Tips website arrow selector tool at 70lb-74lb using a 28" arrow calls out 300 spine, using a 29" arrow calls out a 250 spine. The other problem I have is a 250 spine greatly increases overall weight and drops my foc slightly. Not so worried about slight foc loss, but is the added weight worth the loss of fps? Im a numbers guys so I might just be over thinking this. Any help or suggestions would be appreciated!!!!!  

 

250 spine @ 28.5" 150 grain tip = 497 grain total / 11.6% foc

300 spine @ 28.5" 150 grain tip = 460 grain total / 12.6% foc

 

[NOTAGS]

I would pay more attention to the Kinetic energy in the arrow.  You will have to have arrow velocity for that though.  Perhaps your local pro shop has some arrows close to your weights and a chrono to let you use.

[MULEPACKHUNTER]

I'm shooting 29 in arrows with 150 up front at 68 lbs 340 spine and they shoot great. I think splitting hairs on spine is if your not getting good groups. 

[MULEPACKHUNTER]

How are you going to to get that 150 up front ? 

What broadhead 

what insert

[oz31p]

44 minutes ago, MULEPACKHUNTER said:

I'm shooting 29 in arrows with 150 up front at 68 lbs 340 spine and they shoot great. I think splitting hairs on spine is if your not getting good groups. 

What he said

 

when in doubt go stiffer. If they don’t “group” we have other problems. 

I shoot a similar set up. The best Thing I ever did was stop using calculators. It will drive you mad. 440-500 total. 100bh with a weighted (25-75g brass) make sure they group. Groups equal good flight. True flight with that heavy of an arrow equals 2 holes. 

[MT. CAT]

My grouping right now seems to be good. I was just looking at new arrows and based on the selector tool saying 300/250 I felt like a 340 was maybe too weak.

Is there a difference between using a 150grain BH vs a brass insert and a 100grain BH? 

[MULEPACKHUNTER]

Yes, a 150 broad head will tend to be larger and effect flight more with more surface area. I'm running 100 grn broad heads with brass inserts. 510 grn total weight. 

Only thing I'm looking at now is 3 fletch vs. 4 fletch. 

[MT. CAT]

I was looking at shooting magnus stingers if that helps. Didn’t recall much of a size difference between the sizes but I’m going to look more into that now. 

[MULEPACKHUNTER]

That's funny I'm shooting the same heads. Luckily they are really close to my field points and only off to the right slightly so easy adjustment . Just switched to them last year and they shoot  well but havnt tested on animals yet. Of course there's a lot of opinion out there, little differences like 150 broadhead and light insert vs 100 broadhead and brass insert end up being how do they shoot in the end. 

I agree the size difference is slight from the 100 to the 150 and cutting will be also bigger but slight. Hard to say either way is "the way " just happens I went 100 grn broadhead and brass

[MULEPACKHUNTER]

I have 7 gold tip hunters cut at 28 3/4 for 10 bucks if you want to try your set up ?? Let me know , I can put brass up front and re fletch also if you want to test some other stuff. 

[MULEPACKHUNTER]

Looks to me like I'm going 4 fletch , arrow weight ended up at 524 on the dot. Brass insert and 100 heads. Added a 7 in custom wrap on the back end and man do these hit hard and with tight groups. Super quiet vs what I started off shooting. 

30 yard group