Hi Phil and welcome to the site. Congratulations on your new rifle. Are you going to hunt with the rifle or target shoot?
For some Long Range means 200 to 500 yards as compared to the 100 Yard Hunting Rifle. Your 26' Barrel with a large case round, will allow more powder to be burned before the projectile leaves the muzzle.
Long range for me is 600 / 800 and 1,000 yards, which would be for F-Class, Palma and Long Range Bench Rest.
There are suppliers of Match Grade Ammo out there. Check Lapua and AtlantaArms to see what you can get. They are pricey.
To really get the most out of your rifle, you need to reload. Other than that, you need to try different ammos and see which your rifle likes the most. An ammo that is great in one rifle may not be so good in another. Differences in Barrel Harmonics, Rifling Cuts etc.
The Remington 700 is one of the better Out of The Box bolt action rifles and most will get 1 MOA (approximately 1" at 100 yard) groups when you fine the right ammo or reload it.
Custom rifles in more precise calibers / cartridges can get single hole groups at 100 yards, 6PPC etc. Or 3" groups at 1,000 Yards, 6.5x47L, .338 Lapua. 30mmWSM etc.
What twist rate is in your rifle? That is the first place to start with regard to ammo. Slow Twists usually are best with lighter bullets where heavy high BC projectiles need a fast twist to stabilize. My short range Bench rest rifles have barrels with twist from about 1:13 to 1:14 while my Long Range rifles have twists of 1:8 or 1:7.5
If you really want to ring everything out of your rifle, with the action as it is (not trued) and the factory barrel, I would suggest the following upgrades in the order listed:
First, Replace the Trigger. Minimum Timney, next up is a Timney CE (Calvon Elite) than a Jewel and last a Big-N-Andy . All depends on your budget.
Second, Bed the action and free float the barrel.
After that I would do a lot of shooting and ammo testing or reload testing.
For most the next step would be a better than factory stock and if your want to go all out a truing of the action and competition grade barrel. If you do all of that though, a custom build from the start would be the more practical way to go, but I highly recommend the first two steps above.
You can find Stand Up rifles holders (some based on photo tripods) at places like MidwayUSA.com You will not get the best accuracy shooting that way. A bench with a good rest or a bipod prone or on a bench will do better.
Hope some of this helps. Let us know where you are, what kind of shooting you do and what kind you will be doing with this rifle.