[phreanix]

Have you tried putting it online with a paypal donate button? That's worked wonders for our site and we make more than enough to break even. You'll find that firearms enthusiasts are generally a generous and thankful bunch and if you phrase a request for donation the right way they'll be more than happy to contribute towards your expenses.

I know of one who made a similar app for airgun users that is free but has nag screens but most everyone I know on the airgun forums have shot over (excuse the pun) the small fee to get rid of them out of gratitude for the app, which we all have found quite useful.

http://www.chairgun.com/offset/chairgun2.htm