Depending on what the "wrong" ammo is, it may not be that difficult to find someone to trade with you
Ammo can be shipped, it just needs to be declared as such and carry the correct markings(ORM-D). It also has to go UPS or FED-EX, and both have some specific requirements about where you can drop it off. The few times I've shipped ammo, I took it to the UPS hub in town and was able to ship without incident.
A good start might be to post a list of what you have here...perhaps as a wanted to sell or wanted to trade ad.
Or buy a gun in the calibers for which you already have ammo