I hate to burst your bubble, but as mentioned of RFC there aren't any low cost actions for a competition BR gun. Your potentially cheapest option is to find a screaming deal on a rough 40x and have it blueprinted, but then you are up to close to where you are just buying a new Holeshot Lonestar that is ready to go as mentioned above.
What is a price you are willing to pay? $600 isn't going to buy you an action. Just trying to be realistic with you. Are you planning to really compete or are you just looking to build a nice gun?
