At least long enough that you don't draw it off the rest at full draw, but I'd stay around 27" anyway. A longer shaft is slightly more stabile in flight than a short one.
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Martin Silver Star Shooter
UBP Life Member
PSAA Life Member
Worldwide Scuba Diver
A general rule is 1 inch past the riser at full draw.
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Arrows and Words. Use them wisely, once released they can't be brought back.
Chris Miles
Ulitmate Camo Web Site http://ultimatecamo.com/ UltimateCamo Water Transfer Imaging http://liquidprintone.com/
I agree with BGfisher, I would cut them somewhere around 27 in most cases your arrows end up about 1" to 1/2" less than your draw length.
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"If guns kill people then I can blame my pencil on mispelled words" Larry The Cable Guy
PA Game Commisssion Bowhunter Education Instructor
United Bowhunters of PA
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