I'm not sure from your post which type of lathe you are referring to. To some people, Mini Lathe implies one of the small lathes designed for wood turnings such as pens and such, to others it is typically referring to the Asian 7x10's and 7x12 metal lathes that are widely available. Since I can't think of too many applications for the wood lathe in gunsmithing, I am assuming you are referring to a metal lathe.
Actually right now you have several options available to you. The Asian 7x10 and 7x12's are widely available for under $500 and most come with a decent assortment of tooling, if you need more, and you will, check out the
[url] www.littlemachineshop.com[/url] website for an almost endless assortment of accessories and modifications for these little guys. The lathes are somewhat crude, but they can be refined to a considerable degree and made to perform very nicely, there are many websites available to help you on this project should you choose to go that route. Last year I purchased two of the 7x12 lathes from Cummins for the University that I work at, we needed a small lathe for smaller projects and did not have a lot of money in our budget so they seemed like a good idea. I have since used them extensively in two of the classes that I teach and estimate that more than 60 students have worked on them over the course of the two semesters, they have held up very well.
If you don't want to worry about having to do some modifications you can check out Sherline for their excellent line of American made products. I have one of their short bed metal lathes and it is a very precise machine, but will not handle work as large as the 7x12 lathes will, it is, however, better quality. These lathes start around $600 and again there is numerous tooling available for them.
Both of the above lathes have variable speed motors and would be more than adequate for most small turning tasks, if you wanted to turn muzzleloading pistol barrels I would go with the 7x12 personally. For smaller, more delicate work like screws, pins, and such go with the Sherline.
You might also have some luck checking out Ebay and purchasing an older used lathe such as a 6" Atlas or even perhaps the older Dunlap lathes (not as good as the Atlas) for less than a new lathe. Keep in mind with an older machine that accessories are sometimes hard to find and could get very expensive, do your research before you buy.
Hope this helps.
Alex