new arrows
 

im switching to easton flatlines and want to know if i need 340 or 400. im shooting an hf cam x force at 63lbs and a 27.5 inch arrow and 100 grain heads better speed with 400's but what about the spine??

Archer's Advantage shows the 400's being way too weak for your set and 27.5" 340's being just a tad too stiff. I am assuming you are shooting a 28" dl. Cutting the 340 shafts to 28" will weaken the spine just enough to make you just about perfect.

I'd shoot the 400's I shot 27.5" 400 shafts out of my 70# Allegiance and they tuned like a dream.

They are probably close, but IMO you would be Ok. If you have access to an arrow in 400 and 340 and shoot them both to determine which is best would be ideal.

Otherwise you might be better off playing it safe with the 340's

Dan