I'd say that a trip to the range, 1 box of ammo. Is alot faster and cheaper than spending money and waiting for a custom barrel. Especially if you're just trying to see if the rifle is capable of accomplishing what you want to do with it. Most factory rifles can outshoot beginner users anyway. Also no one just wakes up one day and starts slinging rounds out to 1000 yards with any kind of accuracy or effectiveness. It takes practice at shorter ranges, in that time you'll figure out if your rifle and YOU are capable of shooting at those kind of distances. Work with what you have now and practice proper techniques. Then go out and spend the money on something that is semi custom or whatever your budget allows. You dont want to spend $4,000 on a rifle and another grand or two on a optic. Only to get frustrated with accuracy and effectiveness because your techniques are not up to speed to extract the potential of a custom built firearm. Thats just my .02 based on having to work on a limited budget. But hell if you've got the dough, make bread.
Either way, welcome to the LR shooting community.