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Discussion Starter #1
Bow: 2015 Hoyt Nitrum Turbo 65# 28" DL
Current Arrow: GT Velocity XT 100gr point, 340 spine, total arrow weight 368gr shooting 308 fps.

I want to go a little heavier for hunting. Was thinking about 5mm FMJ's but that would put my total arrow weight around 446gr, don't want to go that heavy.

Was messing around on the GT website with the FOC calculator and 50gr insert weights that I could add instead of building all new arrows. These are the numbers It gave me.

Current arrow is 368gr and their FOC calculator estimated 10.4% FOC
If I added the 50gr insert weight, total arrow weight would be 418 with an FOC of 14.6%

If I go by the rule of 6.5gr of arrow weight per pound of draw I'd be right in there by adding the 50gr insert.

My biggest question is on the 340 spine. I'm already a little over spined but would my 340 arrows still be good with another 50gr of weight up front?
 

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For hunting, you're not overspined now. Without knowing exact arrow length and using OT2 to verify, I'd say your spine is in the good right now. I like the idea of your added weight and FOC, but that may be a tad weak if you're using fixed broadheads. Being at 65#, should probably be fine. I'm sure somebody will chime in with some actual calculated data for you. What is your arrow length though?
 

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I just went through the same thing, shooting GT Hunter Pro 340 with a 100 grn point. I wanted to add 50 grn FACT weight to the system. I ultimately went to 300 spine Pro to accommodate the addition tip weight.

If your on the edge spine wise with the xtra 50grn, you can look at the chart and see if shortening your 340 arrow will work. Not sure if you have an inch or two to spare on arrow length, wasn't included in your stats list.
 

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Discussion Starter #4
My arrows are cut to 27.25" from insert to shaft end, I know arrow length is measured to the nock throat.
 

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What are you hunting? If you hunting blacktail deer or hogs, I think your set up is fine. If you want to get a little more weight, try the GT f.a.c.t weight system. You can ad as little 10 grains. You have enough speed to handle a little extra foc.
 

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Take a look at the Gold Tip arrow selection chart (doesn't matter which brand arrow you are shooting) they have 3 different point weights listed and you can see the changes that 25 grains will have on a shaft, it's around 3 pounds or 1 inch in arrow length. If your arrows were perfectly spined, 50 additional grains up front would need you to turn your bow down 6 pounds or cut your arrows off 2 inches to increase spine. You can test this by buying some field points in various weights and either paper or bare shaft and see the results, and turn the limb bolts up and down.
 
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