What I would suggest is that you get a box of Berger 115 VLD’s for the 257 Roberts and buy some new cases and some match primers and see if you can tease about half inch groups out of it. I do not know what powder but maybe some Varget or 4350 would be a good place to start. This should reach 1000 yards easily. If the rifle will not hold half inch groups then take it to a benchrest gunsmith and have him look it over. That would be my choice for competition.
I would then find all of the ranges and clubs within a hundred miles and see how many have websites. I would check Benchrest Central and 6mmBR forums for matches. What I would look for are “fun” type of competitions such as dynamite, balloon, groundhog, etc. Many of these will have factory classes and the distances will be short to intermediate. About 300 to 500 yards will probably be comfortable to you at first and then you can move out to some of the further distances.
There are a lot of things transferable from these kinds of competitions to shooting deer at 300 yards from a box stand. Mostly they will be shooting mechanics such as trigger control and reloading techniques. Any problems with the rifle, such as a too flexible fore end or bad bedding, scope clarity or shooter will be come apparent. Some of us just don’t have the ability to concentrate and pay attention to details that it requires to become really good competitive shooters, but the objective here is not to become an Olympic gold medalist, instead we just want to improve our shooting skills by practicing under controlled conditions and trying to learn from a group of people who have really great shooting skills.
The Smokin Fur Rifle Club