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Discussion Starter · #1 ·
Hi everyone. Without getting too deep into physics I wanted to get an opinion. I have Easton full metal jacket 5mm arrows and I wanted to go to a heavier arrow set up. Nothing too heavy but a 125 grain broadhead and maybe an insert to get the weight up a bit.

I'm shooting an arrow cut to 31 inches and using a Bear Whitetail Pro at 30 inch draw length and 70 lbs. Would adding a 125 grain broadhead with a weighted insert be overloading this arrow at a 340 spine?
 

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surface level, i would think you are already under spined with that shaft length, draw length, and poundage. but i could be wrong. what does the paper tell you for your current setup?

id say go to a 300 spine and see where you are at for weight. FMJs are already pretty heavy. do you have a target total arrow weight?
 

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Discussion Starter · #3 ·
surface level, i would think you are already under spined with that shaft length, draw length, and poundage. but i could be wrong. what does the paper tell you for your current setup?

id say go to a 300 spine and see where you are at for weight. FMJs are already pretty heavy. do you have a target total arrow weight?
Thank you! No real target in mind. I just had two mishaps this season that I felt could have been remedied by a heavier arrow with a little more energy behind it so I was just toying with the idea of a heavier broadhead and maybe even a little more weight with an insert. I just heard guys talking about overloading arrows that didn't have the correct spine.
 

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Spine charts/software would say you're already severely underspined shooting a 31" 340 shaft out of a 70# bow. But if it's working for you now and broadheads are grouping with field points, it may still work with a little more weight on the front. IMO you'd be better off switching to a 300 spine shaft cut to around 29" (or go with 250 spine if you want to keep them at 31").
 

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Thank you! No real target in mind. I just had two mishaps this season that I felt could have been remedied by a heavier arrow with a little more energy behind it so I was just toying with the idea of a heavier broadhead and maybe even a little more weight with an insert. I just heard guys talking about overloading arrows that didn't have the correct spine.
care to share the mishaps?
 

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Discussion Starter · #7 ·
care to share the mishaps?
No problem...I had a deer at 20 yards broadside, easy shot and thought it was a kill shot but the deer reacted weird, got to the arrow and realized a small weed/tree was right in front of it and it must have deflected it just enough to be a total miss...later that season had a similar scenario. Luckily no wounded deer but still got me thinking a heavier arrow set up may help, especially since I'm usually shooting no more then 30 yards.
 

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Discussion Starter · #8 ·
Way under spine. This is with 20 grain insert anfld 125 point.



OK...I don't full understand the chart but good to know I'm way under-spined. So would 300 spine be better then? Also, if I'm at a 30 inch draw what do the stats say a good arrow length would be? Thank you!
 

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Discussion Starter · #9 ·
Spine charts/software would say you're already severely underspined shooting a 31" 340 shaft out of a 70# bow. But if it's working for you now and broadheads are grouping with field points, it may still work with a little more weight on the front. IMO you'd be better off switching to a 300 spine shaft cut to around 29" (or go with 250 spine if you want to keep them at 31").
Good to know. I'm getting good groups but it's been awhile since I've paper tuned. Might be time to go for a 300 spine arrow.
 

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Hi everyone. Without getting too deep into physics I wanted to get an opinion. I have Easton full metal jacket 5mm arrows and I wanted to go to a heavier arrow set up. Nothing too heavy but a 125 grain broadhead and maybe an insert to get the weight up a bit.

I'm shooting an arrow cut to 31 inches and using a Bear Whitetail Pro at 30 inch draw length and 70 lbs. Would adding a 125 grain broadhead with a weighted insert be overloading this arrow at a 340 spine?
Yes, I say the best thing to do with those fmj’s is to sell them, get some 260 spine axis, 75gr HIT insert and shoot a 100 or 125gr head and you will accomplish what you are trying to and have a very tough user friendly arrow
 

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Hi everyone. Without getting too deep into physics I wanted to get an opinion. I have Easton full metal jacket 5mm arrows and I wanted to go to a heavier arrow set up. Nothing too heavy but a 125 grain broadhead and maybe an insert to get the weight up a bit.

I'm shooting an arrow cut to 31 inches and using a Bear Whitetail Pro at 30 inch draw length and 70 lbs. Would adding a 125 grain broadhead with a weighted insert be overloading this arrow at a 340 spine?
I'd say you're hopelessly underspined regardless of point weight.
 

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OK...I don't full understand the chart but good to know I'm way under-spined. So would 300 spine be better then? Also, if I'm at a 30 inch draw what do the stats say a good arrow length would be? Thank you!
For a 300 spine, you're good at 29" arrow, 20 grain insert and 125 point. Any more point weight you need to go 250 spine.
 

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Hi everyone. Without getting too deep into physics I wanted to get an opinion. I have Easton full metal jacket 5mm arrows and I wanted to go to a heavier arrow set up. Nothing too heavy but a 125 grain broadhead and maybe an insert to get the weight up a bit.

I'm shooting an arrow cut to 31 inches and using a Bear Whitetail Pro at 30 inch draw length and 70 lbs. Would adding a 125 grain broadhead with a weighted insert be overloading this arrow at a 340 spine?
I have some 6 year-old, .300 spine, 5 mm FMJ's with standard HIT inserts, cut to 31" (nock throat to front). Back when I bought them, Easton's chart said they were correctly spined for my 335 IBO bow, with 30.5" DL and 125 grain broadheads. Now, their revised chart puts them as marginal to slightly weakly spined at 65-70#. I'm pretty sure 340's would be weak for your setup, especially with heavier inserts.

I didn't like the 5 mm FMJs. It's too hard to get good FOC% with 12+ gpi weights, without going well over 600 grains. I'd shot 608 grain XX78 2317's for decades. The reason I'd switched was to get flatter trajectories, after hitting a limb, so far above my sight pin perspective, that I couldn't notice it dangling there, caused me to miss an otherwise perfect 30 yard shot on a 6x5 Idaho bull. I'd thought FMJs would be a good option, but they ended up defeating my purpose.

I ended up switching to 31" VAP TKO 300s, with 50 grain inserts and 125 grain broadheads--TAW 478 grains. They are noticeably stiffer than the FMJ 300s. They have much better trajectories, and I couldn't find my last arrow that passed through a bull, because it bounced off a rock behind his left shoulder so hard it landed in thick brush, way up the mountain. The bull was stone dead in 15 seconds within sight. I also killed a buck with one this year. The arrow passed through both shoulders. 478 grains is plenty for anything in N. America.
 

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Discussion Starter · #17 ·
I have some 6 year-old, .300 spine, 5 mm FMJ's with standard HIT inserts, cut to 31" (nock throat to front). Back when I bought them, Easton's chart said they were correctly spined for my 335 IBO bow, with 30.5" DL and 125 grain broadheads. Now, their revised chart puts them as marginal to slightly weakly spined at 65-70#. I'm pretty sure 340's would be weak for your setup, especially with heavier inserts.

I didn't like the 5 mm FMJs. It's too hard to get good FOC% with 12+ gpi weights, without going well over 600 grains. I'd shot 608 grain XX78 2317's for decades. The reason I'd switched was to get flatter trajectories, after hitting a limb, so far above my sight pin perspective, that I couldn't notice it dangling there, caused me to miss an otherwise perfect 30 yard shot on a 6x5 Idaho bull. I'd thought FMJs would be a good option, but they ended up defeating my purpose.

I ended up switching to 31" VAP TKO 300s, with 50 grain inserts and 125 grain broadheads--TAW 478 grains. They are noticeably stiffer than the FMJ 300s. They have much better trajectories, and I couldn't find my last arrow that passed through a bull, because it bounced off a rock behind his left shoulder so hard it landed in thick brush, way up the mountain. The bull was stone dead in 15 seconds within sight. I also killed a buck with one this year. The arrow passed through both shoulders. 478 grains is plenty for anything in N. America.
Dang...that sounds like what I need. I shot a buck this fall at 15 yards in the shoulder and didn't even get a pass through and broke the arrow. Time to start shopping around. Thank you.
 

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Dang...that sounds like what I need. I shot a buck this fall at 15 yards in the shoulder and didn't even get a pass through and broke the arrow. Time to start shopping around. Thank you.
what broadhead are you shooting?

No problem...I had a deer at 20 yards broadside, easy shot and thought it was a kill shot but the deer reacted weird, got to the arrow and realized a small weed/tree was right in front of it and it must have deflected it just enough to be a total miss...later that season had a similar scenario. Luckily no wounded deer but still got me thinking a heavier arrow set up may help, especially since I'm usually shooting no more then 30 yards.
honestly. i dont think heavier is going to solve this issue for you. you are already reasonably heavy with a 31" FMJ. if you are shooting a mech, a modestly sized cut on contact point may help, but not solve your issues. crap still happens.

and this is why i asked... i feel like a lot of time archers (myself included) have a bad experience and look for ways to completely avoid their latest catastrophe. maybe a heavier arrow would help. or maybe a lighter arrow would have helped by shooting flatter and just missing the obstruction. see what im saying? dont go looking for a fix to these issues that are just bad luck, youll likely create other issues.

that said, i still think you are under spined. get into a stiffer arrow. i shoot a 300 spine black eagle with 225 up front. 30" draw, 70lbs. i think the IBO on my frankenbow is pretty slow. but i also have my arrows cut significantly shorter than yours. i think you could shorten up a 300 to stiffen the spine. if you like shooting a longer arrow and still want to add weight, definitely go to 280-260 spine. even with 225 up front my total arrow weight is only 500 grain. personally... i like to build an arrow in that 260-280 fps range with a good cut on contact head. and spend the time getting them to fly right. FOC and total arrow weight are not a thought. with our draw length and poundage, and reasonably light GPI shaft is going to weigh plenty for deer and have enough FOC to satisfy everyone but the most extreme crazies.
 

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I shoot a 5mm FMJ myself out of both my 70 pound Hoyt and 80 pound PSE EVL. I'm a 27.5 draw, but cut my arrows to 28.75 because I shoot COC heads and don't want to pinch a finger on the riser.

On both bows, a 300 spine and a 150 grain broadhead,standard HIT inserts brings me to 553 grains. Thats heavy,and both bows paper tune a bullet. The 80 I was worried it would be underspined,but wasn't.

I think you need to start with a 300 spine, and stiffer if you wanna added more front weight @ your super long draw. 340 ? I think you better get to the paper rack and keep your fingers crossed. I doubt they will hold more weight upfront other than a 125 head.
 

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I shoot a 5mm FMJ myself out of both my 70 pound Hoyt and 80 pound PSE EVL. I'm a 27.5 draw, but cut my arrows to 28.75 because I shoot COC heads and don't want to pinch a finger on the riser.

On both bows, a 300 spine and a 150 grain broadhead,standard HIT inserts brings me to 553 grains. Thats heavy,and both bows paper tune a bullet. The 80 I was worried it would be underspined,but wasn't.

I think you need to start with a 300 spine, and stiffer if you wanna added more front weight @ your super long draw. 340 ? I think you better get to the paper rack and keep your fingers crossed. I doubt they will hold more weight upfront other than a 125 head.
If I were shooting 80#, 553 grains would have better trajectories than @ 65-68#. That would make sense.
 
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