Not sure if you can and really not sure why you would need to.

NEVER SHOOT A BARE SHAFT WITH A BROAD HEAD!!!!!

Paul

If the shaft tunes perfect with a field point then why wouldnt it tune with a broadhead?

For one thing a broad head adds a little more length to the set up than a field tip, not much but it does change things. The biggest reason is because the blades on the head add steering to the front of the arrow and counter act the fletching on the back of the arrow. Depending on the head size and design it can make a big difference.

Fixed heads are more sensitive to spine, tuning and form errors because of this. This is why I always suggest lots of FOC and more fletching than you think you need. This makes for a more forgiving set up with fixed blades.

This is why I said above to never shoot fixed blades without fletchings. The steering is now in the front of the arrow, not the back and things can go bad FAST that way.

Its really not that hard to shoot accurately with target tips if you have decent fletching and adequate arrows. Broad head tipped arrows are not nearly as forgiving and need extra attention in set up and tuning. And are more critical of form and shooting technique.

Paul