I think you’re definitely on the right path. I’ve shot my 300 NM out to 2550 with Frank on his range in Ft. Morgan CO (Everyday Sniper Podcast #281 “New Year’s Eve Resolutions 2021-aired Nov 14th 2020).
While most will push to have you build what they did- I think it’s a preference thing, just find a reputable gun builder, use quality parts and get ready to spend both time & money getting it to perform (Load development and fine tuning your shooting fundamentals) If you're new to ELR I recommend getting some specific training. Having said that- once you do get it tamed, the 300 Norma is a solid heavy hitter for intermediate distance ELR shooting.
Personally; I’ve had the following built by Joseph Furrer of Alyeska Precision, Chugiak Alaska:
BAT Machine Model HR Action
Kreiger 30” Barrel 1-9” twist
Zero Compromise ZCO 5-27x56 MPCT1
SPUHR SP-61602 55MOA Mount
Thunder Beast 338 Ultra Suppressor
J Allen JAE700 Long Action Chassis
Bix-n-Andy TacSport Pro 2/Flat trigger
Thunder Beast Bipod
I shoot 230gr Hornady A-Tips @3075fps (86.0grs Vihtavouri N570)
In our rather crowded and competitive shooting community, this rifle has become something of a standard in accuracy and craftsmanship.