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Archeryologist
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So I am considering the HTR for my next bow. Shot it several times and really like it. Here is the question? I ran the specs through shaft selector on OT2 software and I am a little puzzled. 321 IBO, 70 Lbs, 28" draw, 28.5" arrow, 50 grain insert, 100 grain tip, blazers, and no wraps. It says I should use a .400 spine shaft with this setup. Does this not seem weak? Anyone tuned an HTR yet? I would have figured at least .340 or maybe even .300 spine with the 50 grain insert.
 

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I set one up for a guy last week that shot a really weak arrow. It was 70lbs 29"DL 29" arrow with 100 gn point. It would only tune with a 3555.
 

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57# 27" draw and mined tuned great with 330 injexion 28" 125 BH with 4" feathers and blazers. I like heavy arrows and havent tried any other.
 

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I am waiting on mine but i have also wondered about the spine issue with these cams, i was planning on shooting .400 spine at 60lbs -- 27in dl -- with either 85 or 100gr tips but it seems like your saying i would be in the .500 spine, i lost ot2 when my computer crashed and i am hoping to get a newer version soon to be able to play around with ot2, it was very accurate before on alot of my bows.
 

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So I am considering the HTR for my next bow. Shot it several times and really like it. Here is the question? I ran the specs through shaft selector on OT2 software and I am a little puzzled. 321 IBO, 70 Lbs, 28" draw, 28.5" arrow, 50 grain insert, 100 grain tip, blazers, and no wraps. It says I should use a .400 spine shaft with this setup. Does this not seem weak? Anyone tuned an HTR yet? I would have figured at least .340 or maybe even .300 spine with the 50 grain insert.
You must have put something in incorrectly. I just ran the numbers and it spines out perfectly with a 27.5" 340 spine.
 

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I tentatively plan on GT 7595's at 26.5" with 100 grain brass inserts and 125 grain broadheads. Should be good for a 480 grain arrow at about 220 fps. lol
 

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340 is what you need. You "might" get away with a 400. But a 35/55(500) is IMHO dangerously under spined.
 

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The Impartial Archer
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OT2 doesn't ask what the bow is, right? You just entered something in wrong.
 

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you would think for a soft cam bow you would be able to get away with a .400 spine arrow Purdy easy at 29 and under arrow length .
 

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you would think for a soft cam bow you would be able to get away with a .400 spine arrow Purdy easy at 29 and under arrow length .
He's adding a heavy brass insert and shooting 70lbs though. Those two things don't go well with a 400 spine unless the arrow length is under 27".
 

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DaWorm,

The HTR is a 330 IBO per the Mathews website.. Any bow with a 330 IBO would not be considered a soft cam. With your specs, 340 spine would be the way to go.. definitely not a 0.400 or 0.500 spine. Check the OT2 program version number..most current is Vx449. Updating the program doesn't cost anything.

With your specs, 340 spine would be the best start point..assuming a "shaft length" of 27"-28"..definitely not a 0.400 or 0.500 spine.

Most 35/55 (0.500) spine shafts would most likely end up with a total arrow weight under 350grs…unless you loaded it up with heavy vanes and a wrap. Not sure if the Mathews warranty still 5gr/lb DW..weight issue of the 35/55 would be moot if they're OK under 5gr/lb

If you look up the bow in the OT2 database and click the "apply" button, all the specs are sent to the setup page. All you need to do is enter your specifics..DL, DW, etc. Switch the "cam style" to "Use Mfg IBO". Make sure you've set the Percent Let Off value accordingly..65,75, or 85..that will make a difference, too.

Very important is "shaft length" (raw shaft tube length is what OT2 uses)..which is not the same thing as "complete arrow length" (nock groove to point insert).
 

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If he's shooting it with the 85% mods, it's a 321 IBO bow. I wouldn't be jumping to the conclusion that it's a "soft" cam bow because they are round. Has more to do with the IBO and energy transferred to arrow.

OP, according to my software you need the 340 spine. I'll be shooting a 28" 330 spine out of my 29" @ 70LB HTR.
 
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