My question is generally speaking when tuning a bow for every inch you cut off a shaft about how many grains of point weight is a inch equal to in regard to stiffness?  This is assuming the same shaft is used.

ie:  31" shaft + 145 point weight = 30" shaft + 175 point weight?  

I know there is no concrete answer but what's the general rule of thumb?

App. 25 grs.It varies with every setup but that's a general rule of thumb.

Wood weight per inch changes with species and spine weight..higher spined shafts are generally heavier per inch than lower.

Carbon shafts vary a bit too in grains per inch.

Generally wood weighs somewhere around 8-15 grains per inch.

Carbons 7-10+ grains per inch.

The weight gain or loss by cutting an inch or two off ( or even more ) just won't make a big enough difference to worry about.

Honestly..I'm not trying to be a smart ass here...
I'd say the general rule of thumb is cut your shafts to what ever makes them fly right and weigh them later.

OOOoooo
I see how Jim is looking at it...

It's been my experience that an inch makes a bigger difference than 25 grains.

..but I'm not sure how much.

OK maybe a bit of confusion what I'm needing to know is not actual weight but rather getting them to "fly right"  maybe a better way to ask is for instance will a 340 spine (or what ever spine for that matter) at 31" with a 145 head shoot like a 340 spine at 30" with a 175 head?

I was just trying to figure out a general rule for tuning my stuff.

That's what I was talking about but should have said it differently.25 grs of point weight per inch of shaft.

I have heard the same thing as what Jim has said before, BUT for ME and my horrible, sloppy and inconsistent form, it seems like 50grs is equal to and inch for me.  

My 2016s can be shot out of my Huron at 28" 175gr up front OR 29' with 125 up front.  


I can shoot 125 or 150 grain broad heads and it makes no difference what so ever. But if I jump to a 175 i can see a difference.

I tend to pick a point weight with the insert i want and cut the shaft until I get the fletched and unfletched shafts grouping.