Re: Is this worthy platform to build up
First, you must establish what your budget will be for this "precision LR rifle". The reason is you can get out of control very quickly. The old saying in this hobby is "crack cocaine is cheaper than this hobby". Also, you need to know how far you want to push this LR, in terms of actual distance. Is it going to be 1000 yards and less, or more. Also, is it purely for slaying paper and metal gong, or also for hunting purposes?
Having said that, the 243 cartridge is a fine cartridge for long range. It offer some very high BC bullets for a short action. You can just about take any action, well almost any, and the other of components and give them to a good gunsmith and he may be able to give you a good rifle for punching paper. The only drawback to the Ruger action is probably the lack abundant of aftermarket parts to make it the way you want. If you want to drop a large budget for this purpose, then may I suggest going with either a custom, or a high end rifle. Remember that this can be a very expensive science experiment.
Hope that helps.