Budget ring filer ?????

hay guys give me some kinda idea to file fit the rings for my little 340 I dont plan to do but this 1 and didnt want to spend the extra $$$ for a ring filer if not needed..so let me hear how you file rings please...or do I have to just buy the filer?????

Buy one once and you'll have it for life. I bought one from Summit for under 50 bucks.