spine calculator/formula ?

[Mountain State Archer]

Does anyone know approximately what the formula is for reducing arrow spine with heavy tips?  I'm wanting to shoot heavier heads.  For instance, "what grain head would reduce a 65-70 shaft down to 55-60"?  Thanks for any info

AJ

[Fletcher]

Starting from 125 gr, I add 5 lb for a 160 gr and another 5 lb for 200 gr.  The need for more spine seems to start to diminish going up from there.  In your case I'd suggest shooting some 160 and 190 gr field points thru paper and see how they do.

Let us know what you find out.

[Mountain State Archer]

Thanks, I'll try this soon as I can shovel a shooting lane to my target.   I'm snowed in!   TTT

[Mountain State Archer]

Ttt