What exactly is a "Plinking Load"? 1000yards,though not stretching the 338LM's capability is a distance that requires an accurate stick, a skilled shooter and quality ammo.
Have you actually fired this rifle? If not, how do you know that the "accurizing" work being performed has actually worked?
Although Savage barrels are quite good for factory barrels,fitting a quality barrel-ie. Bartlein,Brux etc.,chambering with a match reamer and setting correct headspace is the foundation to build an accurate rifle. Period.
Why Nosler brass? Lapua brass has,without a doubt,been the standard. Excess of 10 loads per case is the norm in my experience. I have fired over 6K rounds since 2006 or so through several 338LM platforms. Personally, I have had barrels chambered from 25 to 30 inches and found that the most important issue is a 1/9" twist if you are using a 300grain bullet.
A preferred load? Go through the reloading depot forum. Many of us have posted loads that work. I've recently said it in a post last week concerning "plinking"- you don't plink with a 338LM-hitting at 1000yards is NOT plinking. Welcome to the community.