Spine, heavy broadheads & tuning ?

[hat creek]

I have a question concerning using heavy broadheads for big game hunting. On the "light bows for hunting elk" thread the discussion centered around adding a heavy broadhead for better penetration. My question is: if you tune your bow to shoot a certain arrow, say a 30" 2016, and the arrow flies perfectly with a 100 grain field point, how do you add a heavy broadhead without changing the spine of the arrow and change the flight of the arrow itself. I am speaking of aluminum arrows in this case.

[McDave]

A heavier broadhead will change the dynamic spine of the arrow, and you will have to either shorten the arrow or replace the arrow with one with a stiffer spine.

It's hard to tune the arrow with a broadhead attached, so you will probably want to find field points that are the same weight as the broadhead you want to use.

Say you want to use 150 grain broadheads.  You can test with 145 grain field points (I don't know why they don't make 150 grain points, but hopefully the extra 5 grains won't make much difference).  You will find that the bare shaft tests weak with the 145 grain points, if it was perfect with 100 grain points.  You can try cutting down your shafts to 29" if that wouldn't be too short for you, and see how that tests.  Or you can use a stiffer shaft, such as a 2018 or a 2117.

[stemen]

I dont know anything about aluminum but i have done ALOT OF EXPERMENTING WITH TIP WEIGHT ON WOOD ARROWS & i know that every 25 to 30grn. of tip changes the spine 5lbs. i hope this will help

[hat creek]

Good info...since turkey season is still a month away, I have time to experiment with the shafts I have (2016) and 125 grain broadheads. Still have lots of time before next blacktail season.