Bench rest action are fitted substantially tighter than even the best stock 700 , most are fit tight enough that blowing dust can cause function issues . To have an Remington action benchrest blue printed and replace the bolt with an oversized bolt to remove some of the tolerances that cause the slop is going to cost as much as the price of a good purpose specific action once the cost of the action and work are added up .

First You need to determine what the end goal with the rifle is . A field rifle and a benchrest gun are different critters and are put together entirely different . Pretty much the only similarity is the desire for the most usable accuracy available within the constraints of the game they play in .

For the field matches You talked about dirt isn't a huge factor at CRC and PWSA but at Raton it's made rifles choke before and will again . A gun / shooter system that shoots reliably 100% of the time to 1/2 MOA will rule the world at any of the field matches in the country . 1/2 MOA at a benchrest match isn't worth burning the powder with 100 yard groups hovering around .1 inch to be competitive .

Knowing where You are headed will make things easier to steer in the right direction . Same thing I tell all the guy's that ask these questions on here , come out to one of the matches and look at stuff and talk to people . Pretty much there is typically 100 plus years of combined experience on the line and you can see what works and what doesn't . The long range game has a very steep and expensive learning curve and learning from other people's mistakes , we all made them too , smooths things out a bunch .