Would a size-changing weapon property be equivalent to a +1?

Question

I am playing a character who will be undergoing size changes on a regular basis. I am interested in an effect which will make my primary weapon (in this case a bow) always be the correct size that I am currently (in case I end up dropping it while in a size different than natural).

I assume that this kind of ability makes the most sense as a weapon property. As much as I would like it to be a cost based ability like adaptive, but should most likely be an enhancement bonus since thats what most weapon properties are. Since keen is a +1 ability, I feel that this ability would be in-line in terms of power.

Would having adaptive size as a +1 weapon enhancement be balanced/fair? Or is it actually something that exists in Pathfinder already?

While researching this I discovered that there is a sizing weapon property in 3.5 which was a +1 bonus. Only it took a standard action for it to change size.

Answer 1

The Giant Hunter's Handbook (Jan. 2015) includes the magic weapon special ability resizing (4,000 gp; 0 lbs.) that says

A resizing weapon instantly shrinks or grows to suit the size of any creature that picks it up unless it is currently wielded by another creature. It reverts to its original size 1 round after it leaves its wielder’s possession.

From what I can gather, the weapon special ability isn't limited to melee weapons. As a relatively new release, the Handbook's information is likely still being readied for inclusion on d20PFSRD.